diff --git a/.php-cs-fixer.php b/.php-cs-fixer.php
index 62d1ac7f74fa..ed2e6cf2bae8 100644
--- a/.php-cs-fixer.php
+++ b/.php-cs-fixer.php
@@ -71,7 +71,7 @@
         'random_api_migration' => true,
         'ternary_to_null_coalescing' => true,
         'phpdoc_to_param_type' => true,
-        //'declare_strict_types' => true,
+        'declare_strict_types' => true,
 
         // TODO php 7.4 migration (one day..)
         // 'phpdoc_to_property_type' => true,
diff --git a/src/Composer/Autoload/AutoloadGenerator.php b/src/Composer/Autoload/AutoloadGenerator.php
index 5485565e0dd0..0ddcc9df1fd4 100644
--- a/src/Composer/Autoload/AutoloadGenerator.php
+++ b/src/Composer/Autoload/AutoloadGenerator.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Autoload/ClassMapGenerator.php b/src/Composer/Autoload/ClassMapGenerator.php
index 84f946440963..fa687d101f3a 100644
--- a/src/Composer/Autoload/ClassMapGenerator.php
+++ b/src/Composer/Autoload/ClassMapGenerator.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Autoload/PhpFileCleaner.php b/src/Composer/Autoload/PhpFileCleaner.php
index f1e6048b25b6..d6a840b6839f 100644
--- a/src/Composer/Autoload/PhpFileCleaner.php
+++ b/src/Composer/Autoload/PhpFileCleaner.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Cache.php b/src/Composer/Cache.php
index 0f8dc6aa4630..c6e2585aaa31 100644
--- a/src/Composer/Cache.php
+++ b/src/Composer/Cache.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/AboutCommand.php b/src/Composer/Command/AboutCommand.php
index 80d9a9caa197..29dc718e7056 100644
--- a/src/Composer/Command/AboutCommand.php
+++ b/src/Composer/Command/AboutCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/ArchiveCommand.php b/src/Composer/Command/ArchiveCommand.php
index db302b8651a2..0a35f6f28f8a 100644
--- a/src/Composer/Command/ArchiveCommand.php
+++ b/src/Composer/Command/ArchiveCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/BaseCommand.php b/src/Composer/Command/BaseCommand.php
index c06e3ffa5b16..930cde9d5fcb 100644
--- a/src/Composer/Command/BaseCommand.php
+++ b/src/Composer/Command/BaseCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/BaseDependencyCommand.php b/src/Composer/Command/BaseDependencyCommand.php
index f1ebe4277b4f..064b26d31c2b 100644
--- a/src/Composer/Command/BaseDependencyCommand.php
+++ b/src/Composer/Command/BaseDependencyCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/CheckPlatformReqsCommand.php b/src/Composer/Command/CheckPlatformReqsCommand.php
index 54e1e9ba171e..6854ee690b23 100644
--- a/src/Composer/Command/CheckPlatformReqsCommand.php
+++ b/src/Composer/Command/CheckPlatformReqsCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/ClearCacheCommand.php b/src/Composer/Command/ClearCacheCommand.php
index e7c15de31293..e2ba384d38b3 100644
--- a/src/Composer/Command/ClearCacheCommand.php
+++ b/src/Composer/Command/ClearCacheCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/ConfigCommand.php b/src/Composer/Command/ConfigCommand.php
index 3285fd3b40c8..b20a4ba81418 100644
--- a/src/Composer/Command/ConfigCommand.php
+++ b/src/Composer/Command/ConfigCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/CreateProjectCommand.php b/src/Composer/Command/CreateProjectCommand.php
index d7da384e43cf..bda43c5fab2b 100644
--- a/src/Composer/Command/CreateProjectCommand.php
+++ b/src/Composer/Command/CreateProjectCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/DependsCommand.php b/src/Composer/Command/DependsCommand.php
index 54fda17a598c..0dbbb03f2cf7 100644
--- a/src/Composer/Command/DependsCommand.php
+++ b/src/Composer/Command/DependsCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/DiagnoseCommand.php b/src/Composer/Command/DiagnoseCommand.php
index 8ed6ed0f46cc..93ef3c22ae5e 100644
--- a/src/Composer/Command/DiagnoseCommand.php
+++ b/src/Composer/Command/DiagnoseCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/DumpAutoloadCommand.php b/src/Composer/Command/DumpAutoloadCommand.php
index 9eb81f69977a..9ec6abed0dbd 100644
--- a/src/Composer/Command/DumpAutoloadCommand.php
+++ b/src/Composer/Command/DumpAutoloadCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/ExecCommand.php b/src/Composer/Command/ExecCommand.php
index ac3ed11ab544..049f6b687a05 100644
--- a/src/Composer/Command/ExecCommand.php
+++ b/src/Composer/Command/ExecCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/FundCommand.php b/src/Composer/Command/FundCommand.php
index c6287dac9d3c..057fea5d6eab 100644
--- a/src/Composer/Command/FundCommand.php
+++ b/src/Composer/Command/FundCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/GlobalCommand.php b/src/Composer/Command/GlobalCommand.php
index 0b5f442cc147..3ec1254271f0 100644
--- a/src/Composer/Command/GlobalCommand.php
+++ b/src/Composer/Command/GlobalCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/HomeCommand.php b/src/Composer/Command/HomeCommand.php
index 798d654dfc6c..dad4e3a7540f 100644
--- a/src/Composer/Command/HomeCommand.php
+++ b/src/Composer/Command/HomeCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/InitCommand.php b/src/Composer/Command/InitCommand.php
index 1d4dea29bc14..f923f692913d 100644
--- a/src/Composer/Command/InitCommand.php
+++ b/src/Composer/Command/InitCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/InstallCommand.php b/src/Composer/Command/InstallCommand.php
index df1edf062ea8..13b6ff400628 100644
--- a/src/Composer/Command/InstallCommand.php
+++ b/src/Composer/Command/InstallCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/LicensesCommand.php b/src/Composer/Command/LicensesCommand.php
index b51292742f99..003538f3a56e 100644
--- a/src/Composer/Command/LicensesCommand.php
+++ b/src/Composer/Command/LicensesCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/OutdatedCommand.php b/src/Composer/Command/OutdatedCommand.php
index 332a4c64e918..9bc2ee48b3f6 100644
--- a/src/Composer/Command/OutdatedCommand.php
+++ b/src/Composer/Command/OutdatedCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/PackageDiscoveryTrait.php b/src/Composer/Command/PackageDiscoveryTrait.php
index a9685ae13d49..d6c13e79f22b 100644
--- a/src/Composer/Command/PackageDiscoveryTrait.php
+++ b/src/Composer/Command/PackageDiscoveryTrait.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/ProhibitsCommand.php b/src/Composer/Command/ProhibitsCommand.php
index 59165f4de16c..6da462084f7b 100644
--- a/src/Composer/Command/ProhibitsCommand.php
+++ b/src/Composer/Command/ProhibitsCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/ReinstallCommand.php b/src/Composer/Command/ReinstallCommand.php
index 926ba983997c..8150bfa22736 100644
--- a/src/Composer/Command/ReinstallCommand.php
+++ b/src/Composer/Command/ReinstallCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/RemoveCommand.php b/src/Composer/Command/RemoveCommand.php
index fdda37df1fc9..0ec091683d18 100644
--- a/src/Composer/Command/RemoveCommand.php
+++ b/src/Composer/Command/RemoveCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/RequireCommand.php b/src/Composer/Command/RequireCommand.php
index 5a65ccec91eb..3f4fa296518e 100644
--- a/src/Composer/Command/RequireCommand.php
+++ b/src/Composer/Command/RequireCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/RunScriptCommand.php b/src/Composer/Command/RunScriptCommand.php
index fc66a9d04e4e..94709f409744 100644
--- a/src/Composer/Command/RunScriptCommand.php
+++ b/src/Composer/Command/RunScriptCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/ScriptAliasCommand.php b/src/Composer/Command/ScriptAliasCommand.php
index 793127f8c07a..4c34368ad237 100644
--- a/src/Composer/Command/ScriptAliasCommand.php
+++ b/src/Composer/Command/ScriptAliasCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/SearchCommand.php b/src/Composer/Command/SearchCommand.php
index 496394a307db..f701e40d91d4 100644
--- a/src/Composer/Command/SearchCommand.php
+++ b/src/Composer/Command/SearchCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/SelfUpdateCommand.php b/src/Composer/Command/SelfUpdateCommand.php
index f8f49405a10e..259abd5dbb5b 100644
--- a/src/Composer/Command/SelfUpdateCommand.php
+++ b/src/Composer/Command/SelfUpdateCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/ShowCommand.php b/src/Composer/Command/ShowCommand.php
index 8b11a8e33156..b115a7f88cce 100644
--- a/src/Composer/Command/ShowCommand.php
+++ b/src/Composer/Command/ShowCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/StatusCommand.php b/src/Composer/Command/StatusCommand.php
index 58b6663a719a..7721a6501453 100644
--- a/src/Composer/Command/StatusCommand.php
+++ b/src/Composer/Command/StatusCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/SuggestsCommand.php b/src/Composer/Command/SuggestsCommand.php
index eae73a05c15f..23776abb5ba2 100644
--- a/src/Composer/Command/SuggestsCommand.php
+++ b/src/Composer/Command/SuggestsCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/UpdateCommand.php b/src/Composer/Command/UpdateCommand.php
index 2250f225af16..156ac35d91b7 100644
--- a/src/Composer/Command/UpdateCommand.php
+++ b/src/Composer/Command/UpdateCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Command/ValidateCommand.php b/src/Composer/Command/ValidateCommand.php
index e91008f5c138..b1fac8d59f05 100644
--- a/src/Composer/Command/ValidateCommand.php
+++ b/src/Composer/Command/ValidateCommand.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Compiler.php b/src/Composer/Compiler.php
index 02e0ff022cb7..d33f18f9f7e6 100644
--- a/src/Composer/Compiler.php
+++ b/src/Composer/Compiler.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Composer.php b/src/Composer/Composer.php
index a4b769ee2207..93e8c0a6f5d6 100644
--- a/src/Composer/Composer.php
+++ b/src/Composer/Composer.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Config.php b/src/Composer/Config.php
index 18db2918e876..fe3069f54789 100644
--- a/src/Composer/Config.php
+++ b/src/Composer/Config.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Config/ConfigSourceInterface.php b/src/Composer/Config/ConfigSourceInterface.php
index 7cb590de67f7..f94ab630e6e0 100644
--- a/src/Composer/Config/ConfigSourceInterface.php
+++ b/src/Composer/Config/ConfigSourceInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Config/JsonConfigSource.php b/src/Composer/Config/JsonConfigSource.php
index cb04bc6e9a4c..4c031f5d8760 100644
--- a/src/Composer/Config/JsonConfigSource.php
+++ b/src/Composer/Config/JsonConfigSource.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Console/Application.php b/src/Composer/Console/Application.php
index ccb60e6cf291..b5166f9b8ed7 100644
--- a/src/Composer/Console/Application.php
+++ b/src/Composer/Console/Application.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Console/GithubActionError.php b/src/Composer/Console/GithubActionError.php
index d73b55851618..7489a9a389ef 100644
--- a/src/Composer/Console/GithubActionError.php
+++ b/src/Composer/Console/GithubActionError.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Console/HtmlOutputFormatter.php b/src/Composer/Console/HtmlOutputFormatter.php
index f95933a1bbe9..04afda4fcddb 100644
--- a/src/Composer/Console/HtmlOutputFormatter.php
+++ b/src/Composer/Console/HtmlOutputFormatter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Decisions.php b/src/Composer/DependencyResolver/Decisions.php
index f06a25a8b74d..fce11c269c10 100644
--- a/src/Composer/DependencyResolver/Decisions.php
+++ b/src/Composer/DependencyResolver/Decisions.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/DefaultPolicy.php b/src/Composer/DependencyResolver/DefaultPolicy.php
index e7610eb228c0..cdf13f0b0e29 100644
--- a/src/Composer/DependencyResolver/DefaultPolicy.php
+++ b/src/Composer/DependencyResolver/DefaultPolicy.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/GenericRule.php b/src/Composer/DependencyResolver/GenericRule.php
index ab010db0ed0b..b1841466683c 100644
--- a/src/Composer/DependencyResolver/GenericRule.php
+++ b/src/Composer/DependencyResolver/GenericRule.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/LocalRepoTransaction.php b/src/Composer/DependencyResolver/LocalRepoTransaction.php
index 4a03816d7667..06d987797e5c 100644
--- a/src/Composer/DependencyResolver/LocalRepoTransaction.php
+++ b/src/Composer/DependencyResolver/LocalRepoTransaction.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/LockTransaction.php b/src/Composer/DependencyResolver/LockTransaction.php
index 3b3da5df29a5..e9bffab30297 100644
--- a/src/Composer/DependencyResolver/LockTransaction.php
+++ b/src/Composer/DependencyResolver/LockTransaction.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/MultiConflictRule.php b/src/Composer/DependencyResolver/MultiConflictRule.php
index 104d578a821f..63fe1e09ec00 100644
--- a/src/Composer/DependencyResolver/MultiConflictRule.php
+++ b/src/Composer/DependencyResolver/MultiConflictRule.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Operation/InstallOperation.php b/src/Composer/DependencyResolver/Operation/InstallOperation.php
index da31a52cccc1..7869402ab3f7 100644
--- a/src/Composer/DependencyResolver/Operation/InstallOperation.php
+++ b/src/Composer/DependencyResolver/Operation/InstallOperation.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Operation/MarkAliasInstalledOperation.php b/src/Composer/DependencyResolver/Operation/MarkAliasInstalledOperation.php
index 8626813e2571..84d48e3c4fea 100644
--- a/src/Composer/DependencyResolver/Operation/MarkAliasInstalledOperation.php
+++ b/src/Composer/DependencyResolver/Operation/MarkAliasInstalledOperation.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Operation/MarkAliasUninstalledOperation.php b/src/Composer/DependencyResolver/Operation/MarkAliasUninstalledOperation.php
index 1e858ef1e65f..b28e4942c130 100644
--- a/src/Composer/DependencyResolver/Operation/MarkAliasUninstalledOperation.php
+++ b/src/Composer/DependencyResolver/Operation/MarkAliasUninstalledOperation.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Operation/OperationInterface.php b/src/Composer/DependencyResolver/Operation/OperationInterface.php
index 4cc70987d195..45e6acd720d1 100644
--- a/src/Composer/DependencyResolver/Operation/OperationInterface.php
+++ b/src/Composer/DependencyResolver/Operation/OperationInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Operation/SolverOperation.php b/src/Composer/DependencyResolver/Operation/SolverOperation.php
index 094029af0e46..2eb9804baaf6 100644
--- a/src/Composer/DependencyResolver/Operation/SolverOperation.php
+++ b/src/Composer/DependencyResolver/Operation/SolverOperation.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Operation/UninstallOperation.php b/src/Composer/DependencyResolver/Operation/UninstallOperation.php
index 878691508b51..9caa3248cb01 100644
--- a/src/Composer/DependencyResolver/Operation/UninstallOperation.php
+++ b/src/Composer/DependencyResolver/Operation/UninstallOperation.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Operation/UpdateOperation.php b/src/Composer/DependencyResolver/Operation/UpdateOperation.php
index 728bb15116fc..f9f0fd4f5fa3 100644
--- a/src/Composer/DependencyResolver/Operation/UpdateOperation.php
+++ b/src/Composer/DependencyResolver/Operation/UpdateOperation.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/PolicyInterface.php b/src/Composer/DependencyResolver/PolicyInterface.php
index 714041dc0a7d..655ea7191db3 100644
--- a/src/Composer/DependencyResolver/PolicyInterface.php
+++ b/src/Composer/DependencyResolver/PolicyInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Pool.php b/src/Composer/DependencyResolver/Pool.php
index 1abbc6382b89..73a9052b84bc 100644
--- a/src/Composer/DependencyResolver/Pool.php
+++ b/src/Composer/DependencyResolver/Pool.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/PoolBuilder.php b/src/Composer/DependencyResolver/PoolBuilder.php
index 52c831dc569f..676ebfefc1d9 100644
--- a/src/Composer/DependencyResolver/PoolBuilder.php
+++ b/src/Composer/DependencyResolver/PoolBuilder.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/PoolOptimizer.php b/src/Composer/DependencyResolver/PoolOptimizer.php
index 6d9b1dd12452..1304a59414d8 100644
--- a/src/Composer/DependencyResolver/PoolOptimizer.php
+++ b/src/Composer/DependencyResolver/PoolOptimizer.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Problem.php b/src/Composer/DependencyResolver/Problem.php
index 44ad896a9dba..06a2378ab5fe 100644
--- a/src/Composer/DependencyResolver/Problem.php
+++ b/src/Composer/DependencyResolver/Problem.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Request.php b/src/Composer/DependencyResolver/Request.php
index d7cde079377a..e08ae06c70e2 100644
--- a/src/Composer/DependencyResolver/Request.php
+++ b/src/Composer/DependencyResolver/Request.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Rule.php b/src/Composer/DependencyResolver/Rule.php
index 55e75e624768..8909f67fec85 100644
--- a/src/Composer/DependencyResolver/Rule.php
+++ b/src/Composer/DependencyResolver/Rule.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Rule2Literals.php b/src/Composer/DependencyResolver/Rule2Literals.php
index 9545686c8687..bfac6dbfe16f 100644
--- a/src/Composer/DependencyResolver/Rule2Literals.php
+++ b/src/Composer/DependencyResolver/Rule2Literals.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/RuleSet.php b/src/Composer/DependencyResolver/RuleSet.php
index 9d856c4b68f7..69159fd79124 100644
--- a/src/Composer/DependencyResolver/RuleSet.php
+++ b/src/Composer/DependencyResolver/RuleSet.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/RuleSetGenerator.php b/src/Composer/DependencyResolver/RuleSetGenerator.php
index d170db1e3b48..c91141d54ac5 100644
--- a/src/Composer/DependencyResolver/RuleSetGenerator.php
+++ b/src/Composer/DependencyResolver/RuleSetGenerator.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/RuleSetIterator.php b/src/Composer/DependencyResolver/RuleSetIterator.php
index e7afb55d3bb6..3d30c5d7efbb 100644
--- a/src/Composer/DependencyResolver/RuleSetIterator.php
+++ b/src/Composer/DependencyResolver/RuleSetIterator.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/RuleWatchChain.php b/src/Composer/DependencyResolver/RuleWatchChain.php
index f6bab35473b2..f9b90d4a9779 100644
--- a/src/Composer/DependencyResolver/RuleWatchChain.php
+++ b/src/Composer/DependencyResolver/RuleWatchChain.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/RuleWatchGraph.php b/src/Composer/DependencyResolver/RuleWatchGraph.php
index 0b74a9888439..2fea3c43d7b0 100644
--- a/src/Composer/DependencyResolver/RuleWatchGraph.php
+++ b/src/Composer/DependencyResolver/RuleWatchGraph.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/RuleWatchNode.php b/src/Composer/DependencyResolver/RuleWatchNode.php
index d1e027cd2b2d..54e4283c0781 100644
--- a/src/Composer/DependencyResolver/RuleWatchNode.php
+++ b/src/Composer/DependencyResolver/RuleWatchNode.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Solver.php b/src/Composer/DependencyResolver/Solver.php
index 0a07203983af..2c416a95e82b 100644
--- a/src/Composer/DependencyResolver/Solver.php
+++ b/src/Composer/DependencyResolver/Solver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/SolverBugException.php b/src/Composer/DependencyResolver/SolverBugException.php
index 0a8d453ee818..394958a8f6a3 100644
--- a/src/Composer/DependencyResolver/SolverBugException.php
+++ b/src/Composer/DependencyResolver/SolverBugException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/SolverProblemsException.php b/src/Composer/DependencyResolver/SolverProblemsException.php
index 57dfcf00079b..ea8c86af511c 100644
--- a/src/Composer/DependencyResolver/SolverProblemsException.php
+++ b/src/Composer/DependencyResolver/SolverProblemsException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/DependencyResolver/Transaction.php b/src/Composer/DependencyResolver/Transaction.php
index 184855e7389f..c9db082df6ce 100644
--- a/src/Composer/DependencyResolver/Transaction.php
+++ b/src/Composer/DependencyResolver/Transaction.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/ArchiveDownloader.php b/src/Composer/Downloader/ArchiveDownloader.php
index 449593a6b2d2..50c00ac2458a 100644
--- a/src/Composer/Downloader/ArchiveDownloader.php
+++ b/src/Composer/Downloader/ArchiveDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/ChangeReportInterface.php b/src/Composer/Downloader/ChangeReportInterface.php
index a41cce8939ef..857a7f09ef58 100644
--- a/src/Composer/Downloader/ChangeReportInterface.php
+++ b/src/Composer/Downloader/ChangeReportInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/DownloadManager.php b/src/Composer/Downloader/DownloadManager.php
index f34a73d379cf..2aa4c7b2458a 100644
--- a/src/Composer/Downloader/DownloadManager.php
+++ b/src/Composer/Downloader/DownloadManager.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/DownloaderInterface.php b/src/Composer/Downloader/DownloaderInterface.php
index 0b540d4b65b6..5ed8cfc68c93 100644
--- a/src/Composer/Downloader/DownloaderInterface.php
+++ b/src/Composer/Downloader/DownloaderInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/DvcsDownloaderInterface.php b/src/Composer/Downloader/DvcsDownloaderInterface.php
index 45c9b86c5ce5..879aab2edc1a 100644
--- a/src/Composer/Downloader/DvcsDownloaderInterface.php
+++ b/src/Composer/Downloader/DvcsDownloaderInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/FileDownloader.php b/src/Composer/Downloader/FileDownloader.php
index c1858d9b8985..738a386ae231 100644
--- a/src/Composer/Downloader/FileDownloader.php
+++ b/src/Composer/Downloader/FileDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/FilesystemException.php b/src/Composer/Downloader/FilesystemException.php
index f9d4e6fbece4..5aff2f089bb5 100644
--- a/src/Composer/Downloader/FilesystemException.php
+++ b/src/Composer/Downloader/FilesystemException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/FossilDownloader.php b/src/Composer/Downloader/FossilDownloader.php
index 13bd3d25b7c6..d1ae129c30cc 100644
--- a/src/Composer/Downloader/FossilDownloader.php
+++ b/src/Composer/Downloader/FossilDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/GitDownloader.php b/src/Composer/Downloader/GitDownloader.php
index a842a6ea33a2..89a4debab3b8 100644
--- a/src/Composer/Downloader/GitDownloader.php
+++ b/src/Composer/Downloader/GitDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/GzipDownloader.php b/src/Composer/Downloader/GzipDownloader.php
index 8949037ec7f5..60ab50549201 100644
--- a/src/Composer/Downloader/GzipDownloader.php
+++ b/src/Composer/Downloader/GzipDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/HgDownloader.php b/src/Composer/Downloader/HgDownloader.php
index 0537103b1073..c32375c970be 100644
--- a/src/Composer/Downloader/HgDownloader.php
+++ b/src/Composer/Downloader/HgDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/MaxFileSizeExceededException.php b/src/Composer/Downloader/MaxFileSizeExceededException.php
index b7adad1b6d1b..e57e7affded1 100644
--- a/src/Composer/Downloader/MaxFileSizeExceededException.php
+++ b/src/Composer/Downloader/MaxFileSizeExceededException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/PathDownloader.php b/src/Composer/Downloader/PathDownloader.php
index 0cf5d3edf8d3..7749d1fd7928 100644
--- a/src/Composer/Downloader/PathDownloader.php
+++ b/src/Composer/Downloader/PathDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/PerforceDownloader.php b/src/Composer/Downloader/PerforceDownloader.php
index 559d6ba4a67e..785f2fb6aa7c 100644
--- a/src/Composer/Downloader/PerforceDownloader.php
+++ b/src/Composer/Downloader/PerforceDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/PharDownloader.php b/src/Composer/Downloader/PharDownloader.php
index 76517fcd74a5..b70d8e81d733 100644
--- a/src/Composer/Downloader/PharDownloader.php
+++ b/src/Composer/Downloader/PharDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/RarDownloader.php b/src/Composer/Downloader/RarDownloader.php
index ef697d797757..8411f02a2edd 100644
--- a/src/Composer/Downloader/RarDownloader.php
+++ b/src/Composer/Downloader/RarDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/SvnDownloader.php b/src/Composer/Downloader/SvnDownloader.php
index 056add89c842..7e532f4444e5 100644
--- a/src/Composer/Downloader/SvnDownloader.php
+++ b/src/Composer/Downloader/SvnDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/TarDownloader.php b/src/Composer/Downloader/TarDownloader.php
index 92998aac65fc..82916611265e 100644
--- a/src/Composer/Downloader/TarDownloader.php
+++ b/src/Composer/Downloader/TarDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/TransportException.php b/src/Composer/Downloader/TransportException.php
index 89719becf4f8..3a9209be45bb 100644
--- a/src/Composer/Downloader/TransportException.php
+++ b/src/Composer/Downloader/TransportException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/VcsCapableDownloaderInterface.php b/src/Composer/Downloader/VcsCapableDownloaderInterface.php
index 38d12c689e0e..8791702764c0 100644
--- a/src/Composer/Downloader/VcsCapableDownloaderInterface.php
+++ b/src/Composer/Downloader/VcsCapableDownloaderInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/VcsDownloader.php b/src/Composer/Downloader/VcsDownloader.php
index 12f5140f57e7..240eb8930b86 100644
--- a/src/Composer/Downloader/VcsDownloader.php
+++ b/src/Composer/Downloader/VcsDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/XzDownloader.php b/src/Composer/Downloader/XzDownloader.php
index 50325603e480..e476f982003d 100644
--- a/src/Composer/Downloader/XzDownloader.php
+++ b/src/Composer/Downloader/XzDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Downloader/ZipDownloader.php b/src/Composer/Downloader/ZipDownloader.php
index e532bdcdd2e7..7fed754f2ee6 100644
--- a/src/Composer/Downloader/ZipDownloader.php
+++ b/src/Composer/Downloader/ZipDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/EventDispatcher/Event.php b/src/Composer/EventDispatcher/Event.php
index a3f2294ef057..06bd006554da 100644
--- a/src/Composer/EventDispatcher/Event.php
+++ b/src/Composer/EventDispatcher/Event.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/EventDispatcher/EventDispatcher.php b/src/Composer/EventDispatcher/EventDispatcher.php
index d0cd437bd66b..118c75f5b8e0 100644
--- a/src/Composer/EventDispatcher/EventDispatcher.php
+++ b/src/Composer/EventDispatcher/EventDispatcher.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/EventDispatcher/EventSubscriberInterface.php b/src/Composer/EventDispatcher/EventSubscriberInterface.php
index 4de66c80b449..fe0c5bd028ab 100644
--- a/src/Composer/EventDispatcher/EventSubscriberInterface.php
+++ b/src/Composer/EventDispatcher/EventSubscriberInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/EventDispatcher/ScriptExecutionException.php b/src/Composer/EventDispatcher/ScriptExecutionException.php
index 2b12ff68d707..3b05a8831f7d 100644
--- a/src/Composer/EventDispatcher/ScriptExecutionException.php
+++ b/src/Composer/EventDispatcher/ScriptExecutionException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Exception/IrrecoverableDownloadException.php b/src/Composer/Exception/IrrecoverableDownloadException.php
index 72a833c72d43..a442786aece0 100644
--- a/src/Composer/Exception/IrrecoverableDownloadException.php
+++ b/src/Composer/Exception/IrrecoverableDownloadException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Exception/NoSslException.php b/src/Composer/Exception/NoSslException.php
index 55c81fea9da9..4696dd3a5725 100644
--- a/src/Composer/Exception/NoSslException.php
+++ b/src/Composer/Exception/NoSslException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Factory.php b/src/Composer/Factory.php
index c6980057c8a9..697a742cbb37 100644
--- a/src/Composer/Factory.php
+++ b/src/Composer/Factory.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Filter/PlatformRequirementFilter/IgnoreAllPlatformRequirementFilter.php b/src/Composer/Filter/PlatformRequirementFilter/IgnoreAllPlatformRequirementFilter.php
index db779c3c1716..6076c0b04eff 100644
--- a/src/Composer/Filter/PlatformRequirementFilter/IgnoreAllPlatformRequirementFilter.php
+++ b/src/Composer/Filter/PlatformRequirementFilter/IgnoreAllPlatformRequirementFilter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilter.php b/src/Composer/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilter.php
index 5a146bfe318b..7e2e7e926f6d 100644
--- a/src/Composer/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilter.php
+++ b/src/Composer/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Filter/PlatformRequirementFilter/IgnoreNothingPlatformRequirementFilter.php b/src/Composer/Filter/PlatformRequirementFilter/IgnoreNothingPlatformRequirementFilter.php
index 882275b41313..0e2651214ffa 100644
--- a/src/Composer/Filter/PlatformRequirementFilter/IgnoreNothingPlatformRequirementFilter.php
+++ b/src/Composer/Filter/PlatformRequirementFilter/IgnoreNothingPlatformRequirementFilter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Filter/PlatformRequirementFilter/PlatformRequirementFilterFactory.php b/src/Composer/Filter/PlatformRequirementFilter/PlatformRequirementFilterFactory.php
index 302bdd915014..b735d13aed46 100644
--- a/src/Composer/Filter/PlatformRequirementFilter/PlatformRequirementFilterFactory.php
+++ b/src/Composer/Filter/PlatformRequirementFilter/PlatformRequirementFilterFactory.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Filter/PlatformRequirementFilter/PlatformRequirementFilterInterface.php b/src/Composer/Filter/PlatformRequirementFilter/PlatformRequirementFilterInterface.php
index de0fc234a5f9..9a80837a2fb5 100644
--- a/src/Composer/Filter/PlatformRequirementFilter/PlatformRequirementFilterInterface.php
+++ b/src/Composer/Filter/PlatformRequirementFilter/PlatformRequirementFilterInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/IO/BaseIO.php b/src/Composer/IO/BaseIO.php
index 807e0ee3a2bf..d7247e411766 100644
--- a/src/Composer/IO/BaseIO.php
+++ b/src/Composer/IO/BaseIO.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/IO/BufferIO.php b/src/Composer/IO/BufferIO.php
index 0e9b44a2594f..ecbb4a3032de 100644
--- a/src/Composer/IO/BufferIO.php
+++ b/src/Composer/IO/BufferIO.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/IO/ConsoleIO.php b/src/Composer/IO/ConsoleIO.php
index b63baca77892..971d52736c9c 100644
--- a/src/Composer/IO/ConsoleIO.php
+++ b/src/Composer/IO/ConsoleIO.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/IO/IOInterface.php b/src/Composer/IO/IOInterface.php
index ba987cc8a390..a1048be8e319 100644
--- a/src/Composer/IO/IOInterface.php
+++ b/src/Composer/IO/IOInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/IO/NullIO.php b/src/Composer/IO/NullIO.php
index 88c4a8c74bba..fd73feec90e5 100644
--- a/src/Composer/IO/NullIO.php
+++ b/src/Composer/IO/NullIO.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer.php b/src/Composer/Installer.php
index 162918a5e488..5153a81dcaa6 100644
--- a/src/Composer/Installer.php
+++ b/src/Composer/Installer.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/BinaryInstaller.php b/src/Composer/Installer/BinaryInstaller.php
index 05f3c0b341e7..fc1d5d7a1f4b 100644
--- a/src/Composer/Installer/BinaryInstaller.php
+++ b/src/Composer/Installer/BinaryInstaller.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/BinaryPresenceInterface.php b/src/Composer/Installer/BinaryPresenceInterface.php
index 61907f7782da..d920b0eccf70 100644
--- a/src/Composer/Installer/BinaryPresenceInterface.php
+++ b/src/Composer/Installer/BinaryPresenceInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/InstallationManager.php b/src/Composer/Installer/InstallationManager.php
index 8200080b3163..261dbb503586 100644
--- a/src/Composer/Installer/InstallationManager.php
+++ b/src/Composer/Installer/InstallationManager.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/InstallerEvent.php b/src/Composer/Installer/InstallerEvent.php
index cafd0dc1b31a..a87ce66a0ee4 100644
--- a/src/Composer/Installer/InstallerEvent.php
+++ b/src/Composer/Installer/InstallerEvent.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/InstallerEvents.php b/src/Composer/Installer/InstallerEvents.php
index d536b459cf61..fc3da51eeb67 100644
--- a/src/Composer/Installer/InstallerEvents.php
+++ b/src/Composer/Installer/InstallerEvents.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/InstallerInterface.php b/src/Composer/Installer/InstallerInterface.php
index 8ddbed4e6d81..a236e07ced6d 100644
--- a/src/Composer/Installer/InstallerInterface.php
+++ b/src/Composer/Installer/InstallerInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/LibraryInstaller.php b/src/Composer/Installer/LibraryInstaller.php
index 7d88a6d9b083..504380913034 100644
--- a/src/Composer/Installer/LibraryInstaller.php
+++ b/src/Composer/Installer/LibraryInstaller.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/MetapackageInstaller.php b/src/Composer/Installer/MetapackageInstaller.php
index ccc71c3fa9df..21ffaa505d8d 100644
--- a/src/Composer/Installer/MetapackageInstaller.php
+++ b/src/Composer/Installer/MetapackageInstaller.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/NoopInstaller.php b/src/Composer/Installer/NoopInstaller.php
index d1aa1fa18255..d31338854192 100644
--- a/src/Composer/Installer/NoopInstaller.php
+++ b/src/Composer/Installer/NoopInstaller.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/PackageEvent.php b/src/Composer/Installer/PackageEvent.php
index 55029fb9319f..e16ca694ca21 100644
--- a/src/Composer/Installer/PackageEvent.php
+++ b/src/Composer/Installer/PackageEvent.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/PackageEvents.php b/src/Composer/Installer/PackageEvents.php
index 852da58ff126..04f51a91f171 100644
--- a/src/Composer/Installer/PackageEvents.php
+++ b/src/Composer/Installer/PackageEvents.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/PluginInstaller.php b/src/Composer/Installer/PluginInstaller.php
index 2dded4eac6cc..48c403d8553b 100644
--- a/src/Composer/Installer/PluginInstaller.php
+++ b/src/Composer/Installer/PluginInstaller.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/ProjectInstaller.php b/src/Composer/Installer/ProjectInstaller.php
index 60c499f95db1..d981680abd43 100644
--- a/src/Composer/Installer/ProjectInstaller.php
+++ b/src/Composer/Installer/ProjectInstaller.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Installer/SuggestedPackagesReporter.php b/src/Composer/Installer/SuggestedPackagesReporter.php
index f2cfafebda7d..315afea5bdcd 100644
--- a/src/Composer/Installer/SuggestedPackagesReporter.php
+++ b/src/Composer/Installer/SuggestedPackagesReporter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Json/JsonFile.php b/src/Composer/Json/JsonFile.php
index fb6485b43733..987de5cbb8c3 100644
--- a/src/Composer/Json/JsonFile.php
+++ b/src/Composer/Json/JsonFile.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Json/JsonFormatter.php b/src/Composer/Json/JsonFormatter.php
index de6882689511..8ea6f75099d6 100644
--- a/src/Composer/Json/JsonFormatter.php
+++ b/src/Composer/Json/JsonFormatter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Json/JsonManipulator.php b/src/Composer/Json/JsonManipulator.php
index 4a8781c648ef..96a188d16f4d 100644
--- a/src/Composer/Json/JsonManipulator.php
+++ b/src/Composer/Json/JsonManipulator.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Json/JsonValidationException.php b/src/Composer/Json/JsonValidationException.php
index 1187b2f99d71..783d471d176c 100644
--- a/src/Composer/Json/JsonValidationException.php
+++ b/src/Composer/Json/JsonValidationException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/AliasPackage.php b/src/Composer/Package/AliasPackage.php
index 332c1fe05ac5..2a7663d2a850 100644
--- a/src/Composer/Package/AliasPackage.php
+++ b/src/Composer/Package/AliasPackage.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Archiver/ArchivableFilesFilter.php b/src/Composer/Package/Archiver/ArchivableFilesFilter.php
index 8af84271d668..b454dca4de45 100644
--- a/src/Composer/Package/Archiver/ArchivableFilesFilter.php
+++ b/src/Composer/Package/Archiver/ArchivableFilesFilter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Archiver/ArchivableFilesFinder.php b/src/Composer/Package/Archiver/ArchivableFilesFinder.php
index 9a53b719eb3e..a4382c029f9f 100644
--- a/src/Composer/Package/Archiver/ArchivableFilesFinder.php
+++ b/src/Composer/Package/Archiver/ArchivableFilesFinder.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Archiver/ArchiveManager.php b/src/Composer/Package/Archiver/ArchiveManager.php
index c7f5def613b1..75d010a1eb6c 100644
--- a/src/Composer/Package/Archiver/ArchiveManager.php
+++ b/src/Composer/Package/Archiver/ArchiveManager.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Archiver/ArchiverInterface.php b/src/Composer/Package/Archiver/ArchiverInterface.php
index f18e8b45f2c5..f19b2c2856f1 100644
--- a/src/Composer/Package/Archiver/ArchiverInterface.php
+++ b/src/Composer/Package/Archiver/ArchiverInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Archiver/BaseExcludeFilter.php b/src/Composer/Package/Archiver/BaseExcludeFilter.php
index 21a8db5d81f9..13b215199136 100644
--- a/src/Composer/Package/Archiver/BaseExcludeFilter.php
+++ b/src/Composer/Package/Archiver/BaseExcludeFilter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Archiver/ComposerExcludeFilter.php b/src/Composer/Package/Archiver/ComposerExcludeFilter.php
index 07d1e162dd06..9806b77c2673 100644
--- a/src/Composer/Package/Archiver/ComposerExcludeFilter.php
+++ b/src/Composer/Package/Archiver/ComposerExcludeFilter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Archiver/GitExcludeFilter.php b/src/Composer/Package/Archiver/GitExcludeFilter.php
index d81dc7693514..2d41e9c08d58 100644
--- a/src/Composer/Package/Archiver/GitExcludeFilter.php
+++ b/src/Composer/Package/Archiver/GitExcludeFilter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Archiver/PharArchiver.php b/src/Composer/Package/Archiver/PharArchiver.php
index f0d3abaf5b95..d7ecf9dbecd6 100644
--- a/src/Composer/Package/Archiver/PharArchiver.php
+++ b/src/Composer/Package/Archiver/PharArchiver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Archiver/ZipArchiver.php b/src/Composer/Package/Archiver/ZipArchiver.php
index 8c7a4e59ca08..59687a2b2bae 100644
--- a/src/Composer/Package/Archiver/ZipArchiver.php
+++ b/src/Composer/Package/Archiver/ZipArchiver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/BasePackage.php b/src/Composer/Package/BasePackage.php
index 3ab352f6b921..b815aec53d9e 100644
--- a/src/Composer/Package/BasePackage.php
+++ b/src/Composer/Package/BasePackage.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Comparer/Comparer.php b/src/Composer/Package/Comparer/Comparer.php
index d9d5a20f10ca..a2dd890bbded 100644
--- a/src/Composer/Package/Comparer/Comparer.php
+++ b/src/Composer/Package/Comparer/Comparer.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/CompleteAliasPackage.php b/src/Composer/Package/CompleteAliasPackage.php
index f69ad6298e7b..78106fa3c8dc 100644
--- a/src/Composer/Package/CompleteAliasPackage.php
+++ b/src/Composer/Package/CompleteAliasPackage.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/CompletePackage.php b/src/Composer/Package/CompletePackage.php
index 666f3b0c749f..fc706cfe9380 100644
--- a/src/Composer/Package/CompletePackage.php
+++ b/src/Composer/Package/CompletePackage.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/CompletePackageInterface.php b/src/Composer/Package/CompletePackageInterface.php
index 35db9e3cb2fc..c6198dfe6efb 100644
--- a/src/Composer/Package/CompletePackageInterface.php
+++ b/src/Composer/Package/CompletePackageInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Dumper/ArrayDumper.php b/src/Composer/Package/Dumper/ArrayDumper.php
index e5ca23985499..d150504e66e6 100644
--- a/src/Composer/Package/Dumper/ArrayDumper.php
+++ b/src/Composer/Package/Dumper/ArrayDumper.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Link.php b/src/Composer/Package/Link.php
index 1430cd800715..59bfb993fdf1 100644
--- a/src/Composer/Package/Link.php
+++ b/src/Composer/Package/Link.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Loader/ArrayLoader.php b/src/Composer/Package/Loader/ArrayLoader.php
index 5184eb01f487..abebb4163b30 100644
--- a/src/Composer/Package/Loader/ArrayLoader.php
+++ b/src/Composer/Package/Loader/ArrayLoader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Loader/InvalidPackageException.php b/src/Composer/Package/Loader/InvalidPackageException.php
index 80c713544cc5..d021564ad156 100644
--- a/src/Composer/Package/Loader/InvalidPackageException.php
+++ b/src/Composer/Package/Loader/InvalidPackageException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Loader/JsonLoader.php b/src/Composer/Package/Loader/JsonLoader.php
index 4bfeaff8b8ba..3ad5787b10a8 100644
--- a/src/Composer/Package/Loader/JsonLoader.php
+++ b/src/Composer/Package/Loader/JsonLoader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Loader/LoaderInterface.php b/src/Composer/Package/Loader/LoaderInterface.php
index be2e4704237b..cbf1b4c342a6 100644
--- a/src/Composer/Package/Loader/LoaderInterface.php
+++ b/src/Composer/Package/Loader/LoaderInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Loader/RootPackageLoader.php b/src/Composer/Package/Loader/RootPackageLoader.php
index 89eb276368e3..c4c3450658e6 100644
--- a/src/Composer/Package/Loader/RootPackageLoader.php
+++ b/src/Composer/Package/Loader/RootPackageLoader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Loader/ValidatingArrayLoader.php b/src/Composer/Package/Loader/ValidatingArrayLoader.php
index 9fb4a19cd847..cce97be794ce 100644
--- a/src/Composer/Package/Loader/ValidatingArrayLoader.php
+++ b/src/Composer/Package/Loader/ValidatingArrayLoader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Locker.php b/src/Composer/Package/Locker.php
index 6dc77cf5bfad..bb780bb54fef 100644
--- a/src/Composer/Package/Locker.php
+++ b/src/Composer/Package/Locker.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Package.php b/src/Composer/Package/Package.php
index 90dc0688fdb6..e004ca677a8f 100644
--- a/src/Composer/Package/Package.php
+++ b/src/Composer/Package/Package.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/PackageInterface.php b/src/Composer/Package/PackageInterface.php
index e666e7139d0a..e31abef2925e 100644
--- a/src/Composer/Package/PackageInterface.php
+++ b/src/Composer/Package/PackageInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/RootAliasPackage.php b/src/Composer/Package/RootAliasPackage.php
index 7c780189fae5..eaa71fd11909 100644
--- a/src/Composer/Package/RootAliasPackage.php
+++ b/src/Composer/Package/RootAliasPackage.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/RootPackage.php b/src/Composer/Package/RootPackage.php
index a0b7ec950516..bf227eb4452d 100644
--- a/src/Composer/Package/RootPackage.php
+++ b/src/Composer/Package/RootPackage.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/RootPackageInterface.php b/src/Composer/Package/RootPackageInterface.php
index 9e74e4ddc8f3..ad182857062d 100644
--- a/src/Composer/Package/RootPackageInterface.php
+++ b/src/Composer/Package/RootPackageInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Version/StabilityFilter.php b/src/Composer/Package/Version/StabilityFilter.php
index 4280d7499d0d..172901d44931 100644
--- a/src/Composer/Package/Version/StabilityFilter.php
+++ b/src/Composer/Package/Version/StabilityFilter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Version/VersionGuesser.php b/src/Composer/Package/Version/VersionGuesser.php
index 30961de4be97..7e7a0cae1f8d 100644
--- a/src/Composer/Package/Version/VersionGuesser.php
+++ b/src/Composer/Package/Version/VersionGuesser.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Version/VersionParser.php b/src/Composer/Package/Version/VersionParser.php
index 6c0345999069..ca0a117731a9 100644
--- a/src/Composer/Package/Version/VersionParser.php
+++ b/src/Composer/Package/Version/VersionParser.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Package/Version/VersionSelector.php b/src/Composer/Package/Version/VersionSelector.php
index cc8fe238239e..f1cfeafc5efd 100644
--- a/src/Composer/Package/Version/VersionSelector.php
+++ b/src/Composer/Package/Version/VersionSelector.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/PartialComposer.php b/src/Composer/PartialComposer.php
index 8911750662a1..b5c859ae9074 100644
--- a/src/Composer/PartialComposer.php
+++ b/src/Composer/PartialComposer.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Platform/HhvmDetector.php b/src/Composer/Platform/HhvmDetector.php
index 2785d26c4876..f6c5829b6b4d 100644
--- a/src/Composer/Platform/HhvmDetector.php
+++ b/src/Composer/Platform/HhvmDetector.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Platform/Runtime.php b/src/Composer/Platform/Runtime.php
index 6ccdbf546b07..725c3dbbcfce 100644
--- a/src/Composer/Platform/Runtime.php
+++ b/src/Composer/Platform/Runtime.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Platform/Version.php b/src/Composer/Platform/Version.php
index 0731a1cec0b1..1ad22c3ed2af 100644
--- a/src/Composer/Platform/Version.php
+++ b/src/Composer/Platform/Version.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/Capability/Capability.php b/src/Composer/Plugin/Capability/Capability.php
index b12410608947..b2237b44b806 100644
--- a/src/Composer/Plugin/Capability/Capability.php
+++ b/src/Composer/Plugin/Capability/Capability.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/Capability/CommandProvider.php b/src/Composer/Plugin/Capability/CommandProvider.php
index 0f94bf37c231..884b9554d4e3 100644
--- a/src/Composer/Plugin/Capability/CommandProvider.php
+++ b/src/Composer/Plugin/Capability/CommandProvider.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/Capable.php b/src/Composer/Plugin/Capable.php
index 48ae4225021f..9a45833c8077 100644
--- a/src/Composer/Plugin/Capable.php
+++ b/src/Composer/Plugin/Capable.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/CommandEvent.php b/src/Composer/Plugin/CommandEvent.php
index 03d621eb5454..d861671c033f 100644
--- a/src/Composer/Plugin/CommandEvent.php
+++ b/src/Composer/Plugin/CommandEvent.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/PluginEvents.php b/src/Composer/Plugin/PluginEvents.php
index c2e58d510f36..5a82018c0970 100644
--- a/src/Composer/Plugin/PluginEvents.php
+++ b/src/Composer/Plugin/PluginEvents.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/PluginInterface.php b/src/Composer/Plugin/PluginInterface.php
index ae5139a849d2..e5982fdf5918 100644
--- a/src/Composer/Plugin/PluginInterface.php
+++ b/src/Composer/Plugin/PluginInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/PluginManager.php b/src/Composer/Plugin/PluginManager.php
index 537f3b6ecc5d..87a2faf23798 100644
--- a/src/Composer/Plugin/PluginManager.php
+++ b/src/Composer/Plugin/PluginManager.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/PostFileDownloadEvent.php b/src/Composer/Plugin/PostFileDownloadEvent.php
index 5fecd9b0155a..a19a9e38efd5 100644
--- a/src/Composer/Plugin/PostFileDownloadEvent.php
+++ b/src/Composer/Plugin/PostFileDownloadEvent.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/PreCommandRunEvent.php b/src/Composer/Plugin/PreCommandRunEvent.php
index bb0d9a9a4ff7..4afd03a338f4 100644
--- a/src/Composer/Plugin/PreCommandRunEvent.php
+++ b/src/Composer/Plugin/PreCommandRunEvent.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/PreFileDownloadEvent.php b/src/Composer/Plugin/PreFileDownloadEvent.php
index 762952840abe..53fd54f4a33f 100644
--- a/src/Composer/Plugin/PreFileDownloadEvent.php
+++ b/src/Composer/Plugin/PreFileDownloadEvent.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Plugin/PrePoolCreateEvent.php b/src/Composer/Plugin/PrePoolCreateEvent.php
index c647378ac8cf..dee00e4d503d 100644
--- a/src/Composer/Plugin/PrePoolCreateEvent.php
+++ b/src/Composer/Plugin/PrePoolCreateEvent.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Question/StrictConfirmationQuestion.php b/src/Composer/Question/StrictConfirmationQuestion.php
index c656a6126227..b815675c6b6f 100644
--- a/src/Composer/Question/StrictConfirmationQuestion.php
+++ b/src/Composer/Question/StrictConfirmationQuestion.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/ArrayRepository.php b/src/Composer/Repository/ArrayRepository.php
index d1a10e3ea287..0f8e101bdcc5 100644
--- a/src/Composer/Repository/ArrayRepository.php
+++ b/src/Composer/Repository/ArrayRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/ArtifactRepository.php b/src/Composer/Repository/ArtifactRepository.php
index 0739ba1bcfaf..e796739d0849 100644
--- a/src/Composer/Repository/ArtifactRepository.php
+++ b/src/Composer/Repository/ArtifactRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/ComposerRepository.php b/src/Composer/Repository/ComposerRepository.php
index 22f8c5548ff9..72005682b2aa 100644
--- a/src/Composer/Repository/ComposerRepository.php
+++ b/src/Composer/Repository/ComposerRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/CompositeRepository.php b/src/Composer/Repository/CompositeRepository.php
index 3d31aa1debdc..d10815c35730 100644
--- a/src/Composer/Repository/CompositeRepository.php
+++ b/src/Composer/Repository/CompositeRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/ConfigurableRepositoryInterface.php b/src/Composer/Repository/ConfigurableRepositoryInterface.php
index 46a535830d4d..a56540f03454 100644
--- a/src/Composer/Repository/ConfigurableRepositoryInterface.php
+++ b/src/Composer/Repository/ConfigurableRepositoryInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/FilesystemRepository.php b/src/Composer/Repository/FilesystemRepository.php
index 81745ed7bc86..cd677c18fc1a 100644
--- a/src/Composer/Repository/FilesystemRepository.php
+++ b/src/Composer/Repository/FilesystemRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/FilterRepository.php b/src/Composer/Repository/FilterRepository.php
index db678a3f3d73..5072e1696b41 100644
--- a/src/Composer/Repository/FilterRepository.php
+++ b/src/Composer/Repository/FilterRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/InstalledArrayRepository.php b/src/Composer/Repository/InstalledArrayRepository.php
index d046a9973f51..971276fbdb4b 100644
--- a/src/Composer/Repository/InstalledArrayRepository.php
+++ b/src/Composer/Repository/InstalledArrayRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/InstalledFilesystemRepository.php b/src/Composer/Repository/InstalledFilesystemRepository.php
index ac8bef79ab39..393a384229af 100644
--- a/src/Composer/Repository/InstalledFilesystemRepository.php
+++ b/src/Composer/Repository/InstalledFilesystemRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/InstalledRepository.php b/src/Composer/Repository/InstalledRepository.php
index c3157372164d..2c3231a9d908 100644
--- a/src/Composer/Repository/InstalledRepository.php
+++ b/src/Composer/Repository/InstalledRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/InstalledRepositoryInterface.php b/src/Composer/Repository/InstalledRepositoryInterface.php
index a25d7369e2e7..3b89d1da2d8e 100644
--- a/src/Composer/Repository/InstalledRepositoryInterface.php
+++ b/src/Composer/Repository/InstalledRepositoryInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/InvalidRepositoryException.php b/src/Composer/Repository/InvalidRepositoryException.php
index 061a5048b51b..9dbd6f0de857 100644
--- a/src/Composer/Repository/InvalidRepositoryException.php
+++ b/src/Composer/Repository/InvalidRepositoryException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/LockArrayRepository.php b/src/Composer/Repository/LockArrayRepository.php
index ddccdd0b14aa..2203525c32fb 100644
--- a/src/Composer/Repository/LockArrayRepository.php
+++ b/src/Composer/Repository/LockArrayRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/PackageRepository.php b/src/Composer/Repository/PackageRepository.php
index f0ed385ee49f..4fbadccef328 100644
--- a/src/Composer/Repository/PackageRepository.php
+++ b/src/Composer/Repository/PackageRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/PathRepository.php b/src/Composer/Repository/PathRepository.php
index dcb9c82d54a7..5241e0015d11 100644
--- a/src/Composer/Repository/PathRepository.php
+++ b/src/Composer/Repository/PathRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/PearRepository.php b/src/Composer/Repository/PearRepository.php
index 0998f302dd98..facc417878f0 100644
--- a/src/Composer/Repository/PearRepository.php
+++ b/src/Composer/Repository/PearRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/PlatformRepository.php b/src/Composer/Repository/PlatformRepository.php
index 6d8afe4a1c82..d31e0ede26f6 100644
--- a/src/Composer/Repository/PlatformRepository.php
+++ b/src/Composer/Repository/PlatformRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/RepositoryFactory.php b/src/Composer/Repository/RepositoryFactory.php
index 25e86aa52a72..b31f77530689 100644
--- a/src/Composer/Repository/RepositoryFactory.php
+++ b/src/Composer/Repository/RepositoryFactory.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/RepositoryInterface.php b/src/Composer/Repository/RepositoryInterface.php
index 129a0949879a..9b612f610890 100644
--- a/src/Composer/Repository/RepositoryInterface.php
+++ b/src/Composer/Repository/RepositoryInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/RepositoryManager.php b/src/Composer/Repository/RepositoryManager.php
index 0f119931ee7b..c09fe1421008 100644
--- a/src/Composer/Repository/RepositoryManager.php
+++ b/src/Composer/Repository/RepositoryManager.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/RepositorySecurityException.php b/src/Composer/Repository/RepositorySecurityException.php
index b115d9cbeb12..c4323145c714 100644
--- a/src/Composer/Repository/RepositorySecurityException.php
+++ b/src/Composer/Repository/RepositorySecurityException.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/RepositorySet.php b/src/Composer/Repository/RepositorySet.php
index c0e39fd5f2dd..e3ad49dfe0de 100644
--- a/src/Composer/Repository/RepositorySet.php
+++ b/src/Composer/Repository/RepositorySet.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/RootPackageRepository.php b/src/Composer/Repository/RootPackageRepository.php
index e1aa37443cd1..0cce7ec53d42 100644
--- a/src/Composer/Repository/RootPackageRepository.php
+++ b/src/Composer/Repository/RootPackageRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/FossilDriver.php b/src/Composer/Repository/Vcs/FossilDriver.php
index 1fb0fb36bec3..b8b342905425 100644
--- a/src/Composer/Repository/Vcs/FossilDriver.php
+++ b/src/Composer/Repository/Vcs/FossilDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/GitBitbucketDriver.php b/src/Composer/Repository/Vcs/GitBitbucketDriver.php
index 1e045c3e907e..33bee56eb3ce 100644
--- a/src/Composer/Repository/Vcs/GitBitbucketDriver.php
+++ b/src/Composer/Repository/Vcs/GitBitbucketDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/GitDriver.php b/src/Composer/Repository/Vcs/GitDriver.php
index 978db48ecf68..182d2816b2e5 100644
--- a/src/Composer/Repository/Vcs/GitDriver.php
+++ b/src/Composer/Repository/Vcs/GitDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/GitHubDriver.php b/src/Composer/Repository/Vcs/GitHubDriver.php
index 548db6e265bf..ad05de78a736 100644
--- a/src/Composer/Repository/Vcs/GitHubDriver.php
+++ b/src/Composer/Repository/Vcs/GitHubDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/GitLabDriver.php b/src/Composer/Repository/Vcs/GitLabDriver.php
index b581e6c1c710..68988e1e756a 100644
--- a/src/Composer/Repository/Vcs/GitLabDriver.php
+++ b/src/Composer/Repository/Vcs/GitLabDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/HgDriver.php b/src/Composer/Repository/Vcs/HgDriver.php
index 1faa3c3e3b55..70f69cbb3a1a 100644
--- a/src/Composer/Repository/Vcs/HgDriver.php
+++ b/src/Composer/Repository/Vcs/HgDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/PerforceDriver.php b/src/Composer/Repository/Vcs/PerforceDriver.php
index 1caad14a7557..92459fdab32f 100644
--- a/src/Composer/Repository/Vcs/PerforceDriver.php
+++ b/src/Composer/Repository/Vcs/PerforceDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/SvnDriver.php b/src/Composer/Repository/Vcs/SvnDriver.php
index 0c028b369704..b4c4064a597a 100644
--- a/src/Composer/Repository/Vcs/SvnDriver.php
+++ b/src/Composer/Repository/Vcs/SvnDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/VcsDriver.php b/src/Composer/Repository/Vcs/VcsDriver.php
index 8656aa69df19..f0c3af1caa81 100644
--- a/src/Composer/Repository/Vcs/VcsDriver.php
+++ b/src/Composer/Repository/Vcs/VcsDriver.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/Vcs/VcsDriverInterface.php b/src/Composer/Repository/Vcs/VcsDriverInterface.php
index 9acf2e7023c6..4a05e8d4b8db 100644
--- a/src/Composer/Repository/Vcs/VcsDriverInterface.php
+++ b/src/Composer/Repository/Vcs/VcsDriverInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/VcsRepository.php b/src/Composer/Repository/VcsRepository.php
index 9978413c748d..41587f5b5d33 100644
--- a/src/Composer/Repository/VcsRepository.php
+++ b/src/Composer/Repository/VcsRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/VersionCacheInterface.php b/src/Composer/Repository/VersionCacheInterface.php
index 93572c10a60d..520007a98a0a 100644
--- a/src/Composer/Repository/VersionCacheInterface.php
+++ b/src/Composer/Repository/VersionCacheInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/WritableArrayRepository.php b/src/Composer/Repository/WritableArrayRepository.php
index 6f98ad18dde6..acf317e0056c 100644
--- a/src/Composer/Repository/WritableArrayRepository.php
+++ b/src/Composer/Repository/WritableArrayRepository.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Repository/WritableRepositoryInterface.php b/src/Composer/Repository/WritableRepositoryInterface.php
index 8e7eac21efcb..46a3c9ea11e2 100644
--- a/src/Composer/Repository/WritableRepositoryInterface.php
+++ b/src/Composer/Repository/WritableRepositoryInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Script/Event.php b/src/Composer/Script/Event.php
index 0f05a72912f1..4b8ba2468d22 100644
--- a/src/Composer/Script/Event.php
+++ b/src/Composer/Script/Event.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Script/ScriptEvents.php b/src/Composer/Script/ScriptEvents.php
index 33cc4f57dd8b..1c40248858ee 100644
--- a/src/Composer/Script/ScriptEvents.php
+++ b/src/Composer/Script/ScriptEvents.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/SelfUpdate/Keys.php b/src/Composer/SelfUpdate/Keys.php
index e8ce93045aa5..72df28fd701a 100644
--- a/src/Composer/SelfUpdate/Keys.php
+++ b/src/Composer/SelfUpdate/Keys.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/SelfUpdate/Versions.php b/src/Composer/SelfUpdate/Versions.php
index ea51319f7089..40301eb20b2b 100644
--- a/src/Composer/SelfUpdate/Versions.php
+++ b/src/Composer/SelfUpdate/Versions.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/AuthHelper.php b/src/Composer/Util/AuthHelper.php
index 54cb83f581ff..39c3691f4701 100644
--- a/src/Composer/Util/AuthHelper.php
+++ b/src/Composer/Util/AuthHelper.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Bitbucket.php b/src/Composer/Util/Bitbucket.php
index b80eb37bec79..970225560e7a 100644
--- a/src/Composer/Util/Bitbucket.php
+++ b/src/Composer/Util/Bitbucket.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/ComposerMirror.php b/src/Composer/Util/ComposerMirror.php
index 26afb80e5428..9fb9f158ce07 100644
--- a/src/Composer/Util/ComposerMirror.php
+++ b/src/Composer/Util/ComposerMirror.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/ConfigValidator.php b/src/Composer/Util/ConfigValidator.php
index ea84c10b299b..3e00b85c70dc 100644
--- a/src/Composer/Util/ConfigValidator.php
+++ b/src/Composer/Util/ConfigValidator.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/ErrorHandler.php b/src/Composer/Util/ErrorHandler.php
index fa2459e2cad0..80a0f9eed806 100644
--- a/src/Composer/Util/ErrorHandler.php
+++ b/src/Composer/Util/ErrorHandler.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Filesystem.php b/src/Composer/Util/Filesystem.php
index c60dd80ec941..6d089017e39a 100644
--- a/src/Composer/Util/Filesystem.php
+++ b/src/Composer/Util/Filesystem.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Git.php b/src/Composer/Util/Git.php
index f28271c74e10..2c9167f56391 100644
--- a/src/Composer/Util/Git.php
+++ b/src/Composer/Util/Git.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/GitHub.php b/src/Composer/Util/GitHub.php
index 4390bb8ac7bc..5d22400e8a77 100644
--- a/src/Composer/Util/GitHub.php
+++ b/src/Composer/Util/GitHub.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/GitLab.php b/src/Composer/Util/GitLab.php
index 97c920ddec66..8f453efaa340 100644
--- a/src/Composer/Util/GitLab.php
+++ b/src/Composer/Util/GitLab.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Hg.php b/src/Composer/Util/Hg.php
index 7797fe1a4083..8c2412239e35 100644
--- a/src/Composer/Util/Hg.php
+++ b/src/Composer/Util/Hg.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Http/CurlDownloader.php b/src/Composer/Util/Http/CurlDownloader.php
index 327c09976b99..df64f074234d 100644
--- a/src/Composer/Util/Http/CurlDownloader.php
+++ b/src/Composer/Util/Http/CurlDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Http/CurlResponse.php b/src/Composer/Util/Http/CurlResponse.php
index c51ff50693cc..41c7037274cf 100644
--- a/src/Composer/Util/Http/CurlResponse.php
+++ b/src/Composer/Util/Http/CurlResponse.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Http/ProxyHelper.php b/src/Composer/Util/Http/ProxyHelper.php
index 49c89c215fd5..a83fd454aca9 100644
--- a/src/Composer/Util/Http/ProxyHelper.php
+++ b/src/Composer/Util/Http/ProxyHelper.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Http/ProxyManager.php b/src/Composer/Util/Http/ProxyManager.php
index df7db9f5f68c..fa91bf7e0b00 100644
--- a/src/Composer/Util/Http/ProxyManager.php
+++ b/src/Composer/Util/Http/ProxyManager.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Http/RequestProxy.php b/src/Composer/Util/Http/RequestProxy.php
index eaf3f9452bd5..36a5fdbabdfe 100644
--- a/src/Composer/Util/Http/RequestProxy.php
+++ b/src/Composer/Util/Http/RequestProxy.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Http/Response.php b/src/Composer/Util/Http/Response.php
index 5556b6754cf5..1c685265c71e 100644
--- a/src/Composer/Util/Http/Response.php
+++ b/src/Composer/Util/Http/Response.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/HttpDownloader.php b/src/Composer/Util/HttpDownloader.php
index b39108724107..b70e0682f434 100644
--- a/src/Composer/Util/HttpDownloader.php
+++ b/src/Composer/Util/HttpDownloader.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/IniHelper.php b/src/Composer/Util/IniHelper.php
index 699f22513c7d..111ad66d5d51 100644
--- a/src/Composer/Util/IniHelper.php
+++ b/src/Composer/Util/IniHelper.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Loop.php b/src/Composer/Util/Loop.php
index 48edc1e16f96..cc4d08c9f453 100644
--- a/src/Composer/Util/Loop.php
+++ b/src/Composer/Util/Loop.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/MetadataMinifier.php b/src/Composer/Util/MetadataMinifier.php
index 6fae871c30ab..ff93821dde42 100644
--- a/src/Composer/Util/MetadataMinifier.php
+++ b/src/Composer/Util/MetadataMinifier.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/NoProxyPattern.php b/src/Composer/Util/NoProxyPattern.php
index 2ae47556105e..857095b667a4 100644
--- a/src/Composer/Util/NoProxyPattern.php
+++ b/src/Composer/Util/NoProxyPattern.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/PackageInfo.php b/src/Composer/Util/PackageInfo.php
index 84277c731cb3..0b2607ac9cac 100644
--- a/src/Composer/Util/PackageInfo.php
+++ b/src/Composer/Util/PackageInfo.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/PackageSorter.php b/src/Composer/Util/PackageSorter.php
index 62889961a4bf..83ae4da37a64 100644
--- a/src/Composer/Util/PackageSorter.php
+++ b/src/Composer/Util/PackageSorter.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Perforce.php b/src/Composer/Util/Perforce.php
index ee21169e107c..65d2a03184e8 100644
--- a/src/Composer/Util/Perforce.php
+++ b/src/Composer/Util/Perforce.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Platform.php b/src/Composer/Util/Platform.php
index 4e58cecbb62c..eb71673a26d9 100644
--- a/src/Composer/Util/Platform.php
+++ b/src/Composer/Util/Platform.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/ProcessExecutor.php b/src/Composer/Util/ProcessExecutor.php
index aa9bb5eaf694..d2572a02eadc 100644
--- a/src/Composer/Util/ProcessExecutor.php
+++ b/src/Composer/Util/ProcessExecutor.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/RemoteFilesystem.php b/src/Composer/Util/RemoteFilesystem.php
index 4d666fc30e34..5aa7d668522c 100644
--- a/src/Composer/Util/RemoteFilesystem.php
+++ b/src/Composer/Util/RemoteFilesystem.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Silencer.php b/src/Composer/Util/Silencer.php
index 484b5a5c7a6c..c01404be6265 100644
--- a/src/Composer/Util/Silencer.php
+++ b/src/Composer/Util/Silencer.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/StreamContextFactory.php b/src/Composer/Util/StreamContextFactory.php
index a4b1dbd4a619..99a5d96c254d 100644
--- a/src/Composer/Util/StreamContextFactory.php
+++ b/src/Composer/Util/StreamContextFactory.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Svn.php b/src/Composer/Util/Svn.php
index 00a090d5c2c9..db5950696cb2 100644
--- a/src/Composer/Util/Svn.php
+++ b/src/Composer/Util/Svn.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/SyncHelper.php b/src/Composer/Util/SyncHelper.php
index c245d2132e70..819115d83e6c 100644
--- a/src/Composer/Util/SyncHelper.php
+++ b/src/Composer/Util/SyncHelper.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Tar.php b/src/Composer/Util/Tar.php
index 05f2229f03b2..489565b1be90 100644
--- a/src/Composer/Util/Tar.php
+++ b/src/Composer/Util/Tar.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/TlsHelper.php b/src/Composer/Util/TlsHelper.php
index 78829e60e47a..95f94887f956 100644
--- a/src/Composer/Util/TlsHelper.php
+++ b/src/Composer/Util/TlsHelper.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Url.php b/src/Composer/Util/Url.php
index 6089da925d7e..c30e4199dd2f 100644
--- a/src/Composer/Util/Url.php
+++ b/src/Composer/Util/Url.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/Composer/Util/Zip.php b/src/Composer/Util/Zip.php
index 342c1d3b724f..20c33771bd79 100644
--- a/src/Composer/Util/Zip.php
+++ b/src/Composer/Util/Zip.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/src/bootstrap.php b/src/bootstrap.php
index 3b2cb4d852f7..886b4ff0cb11 100644
--- a/src/bootstrap.php
+++ b/src/bootstrap.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/AllFunctionalTest.php b/tests/Composer/Test/AllFunctionalTest.php
index a46b49859e76..81ee7b382809 100644
--- a/tests/Composer/Test/AllFunctionalTest.php
+++ b/tests/Composer/Test/AllFunctionalTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/ApplicationTest.php b/tests/Composer/Test/ApplicationTest.php
index 151eca5b4b24..8effc0684b45 100644
--- a/tests/Composer/Test/ApplicationTest.php
+++ b/tests/Composer/Test/ApplicationTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Autoload/AutoloadGeneratorTest.php b/tests/Composer/Test/Autoload/AutoloadGeneratorTest.php
index 6a3fbec83a2f..27c444bec187 100644
--- a/tests/Composer/Test/Autoload/AutoloadGeneratorTest.php
+++ b/tests/Composer/Test/Autoload/AutoloadGeneratorTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Autoload/ClassLoaderTest.php b/tests/Composer/Test/Autoload/ClassLoaderTest.php
index 27f96d6b7a6b..81d6f5fd0b60 100644
--- a/tests/Composer/Test/Autoload/ClassLoaderTest.php
+++ b/tests/Composer/Test/Autoload/ClassLoaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
index 302ab6094a48..f384026208eb 100644
--- a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
+++ b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/CacheTest.php b/tests/Composer/Test/CacheTest.php
index 703650db31ad..62b0d877d836 100644
--- a/tests/Composer/Test/CacheTest.php
+++ b/tests/Composer/Test/CacheTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Command/ArchiveCommandTest.php b/tests/Composer/Test/Command/ArchiveCommandTest.php
index 9ad7bf73f320..0d7b074012dd 100644
--- a/tests/Composer/Test/Command/ArchiveCommandTest.php
+++ b/tests/Composer/Test/Command/ArchiveCommandTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Command/InitCommandTest.php b/tests/Composer/Test/Command/InitCommandTest.php
index f33f730b93a1..ae1a6184c7ae 100644
--- a/tests/Composer/Test/Command/InitCommandTest.php
+++ b/tests/Composer/Test/Command/InitCommandTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Command/RunScriptCommandTest.php b/tests/Composer/Test/Command/RunScriptCommandTest.php
index 200ae7c9a1eb..c52fdb889bda 100644
--- a/tests/Composer/Test/Command/RunScriptCommandTest.php
+++ b/tests/Composer/Test/Command/RunScriptCommandTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/ComposerTest.php b/tests/Composer/Test/ComposerTest.php
index 216245a49da2..2cbd54544b75 100644
--- a/tests/Composer/Test/ComposerTest.php
+++ b/tests/Composer/Test/ComposerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Config/JsonConfigSourceTest.php b/tests/Composer/Test/Config/JsonConfigSourceTest.php
index 818e22db365c..6192fd5a3349 100644
--- a/tests/Composer/Test/Config/JsonConfigSourceTest.php
+++ b/tests/Composer/Test/Config/JsonConfigSourceTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/ConfigTest.php b/tests/Composer/Test/ConfigTest.php
index 924806e606e4..73d20f58a7fd 100644
--- a/tests/Composer/Test/ConfigTest.php
+++ b/tests/Composer/Test/ConfigTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Console/HtmlOutputFormatterTest.php b/tests/Composer/Test/Console/HtmlOutputFormatterTest.php
index 60865f726190..46ab0caab58a 100644
--- a/tests/Composer/Test/Console/HtmlOutputFormatterTest.php
+++ b/tests/Composer/Test/Console/HtmlOutputFormatterTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DefaultConfigTest.php b/tests/Composer/Test/DefaultConfigTest.php
index 0b5f694ea600..a49a98ef80aa 100644
--- a/tests/Composer/Test/DefaultConfigTest.php
+++ b/tests/Composer/Test/DefaultConfigTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/DefaultPolicyTest.php b/tests/Composer/Test/DependencyResolver/DefaultPolicyTest.php
index 27569baee944..4d0c3c136ccd 100644
--- a/tests/Composer/Test/DependencyResolver/DefaultPolicyTest.php
+++ b/tests/Composer/Test/DependencyResolver/DefaultPolicyTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/PoolBuilderTest.php b/tests/Composer/Test/DependencyResolver/PoolBuilderTest.php
index 847b374d4233..7e62491134ef 100644
--- a/tests/Composer/Test/DependencyResolver/PoolBuilderTest.php
+++ b/tests/Composer/Test/DependencyResolver/PoolBuilderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/PoolOptimizerTest.php b/tests/Composer/Test/DependencyResolver/PoolOptimizerTest.php
index 37e7346fc8d3..18ef95dc378f 100644
--- a/tests/Composer/Test/DependencyResolver/PoolOptimizerTest.php
+++ b/tests/Composer/Test/DependencyResolver/PoolOptimizerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/PoolTest.php b/tests/Composer/Test/DependencyResolver/PoolTest.php
index 3d24f9fdfb14..6952955d86c2 100644
--- a/tests/Composer/Test/DependencyResolver/PoolTest.php
+++ b/tests/Composer/Test/DependencyResolver/PoolTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/RequestTest.php b/tests/Composer/Test/DependencyResolver/RequestTest.php
index c3fff4a0e561..a749be8bf4f7 100644
--- a/tests/Composer/Test/DependencyResolver/RequestTest.php
+++ b/tests/Composer/Test/DependencyResolver/RequestTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/RuleSetIteratorTest.php b/tests/Composer/Test/DependencyResolver/RuleSetIteratorTest.php
index 807311882330..7e55c7013138 100644
--- a/tests/Composer/Test/DependencyResolver/RuleSetIteratorTest.php
+++ b/tests/Composer/Test/DependencyResolver/RuleSetIteratorTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/RuleSetTest.php b/tests/Composer/Test/DependencyResolver/RuleSetTest.php
index c891cb9361d7..2912ebc3f5d0 100644
--- a/tests/Composer/Test/DependencyResolver/RuleSetTest.php
+++ b/tests/Composer/Test/DependencyResolver/RuleSetTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/RuleTest.php b/tests/Composer/Test/DependencyResolver/RuleTest.php
index ed140193611e..9bd9e5377594 100644
--- a/tests/Composer/Test/DependencyResolver/RuleTest.php
+++ b/tests/Composer/Test/DependencyResolver/RuleTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/SolverTest.php b/tests/Composer/Test/DependencyResolver/SolverTest.php
index f3782f2fbd4c..a3c2e3d3aced 100644
--- a/tests/Composer/Test/DependencyResolver/SolverTest.php
+++ b/tests/Composer/Test/DependencyResolver/SolverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/DependencyResolver/TransactionTest.php b/tests/Composer/Test/DependencyResolver/TransactionTest.php
index 0f1182d849e1..0cb73d3fc821 100644
--- a/tests/Composer/Test/DependencyResolver/TransactionTest.php
+++ b/tests/Composer/Test/DependencyResolver/TransactionTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Downloader/ArchiveDownloaderTest.php b/tests/Composer/Test/Downloader/ArchiveDownloaderTest.php
index 4b95b2bd919e..c0d4d7ee7477 100644
--- a/tests/Composer/Test/Downloader/ArchiveDownloaderTest.php
+++ b/tests/Composer/Test/Downloader/ArchiveDownloaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Downloader/DownloadManagerTest.php b/tests/Composer/Test/Downloader/DownloadManagerTest.php
index 8ff051927061..f587f703b20e 100644
--- a/tests/Composer/Test/Downloader/DownloadManagerTest.php
+++ b/tests/Composer/Test/Downloader/DownloadManagerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Downloader/FileDownloaderTest.php b/tests/Composer/Test/Downloader/FileDownloaderTest.php
index c147351626cf..8ed93f9ac2a6 100644
--- a/tests/Composer/Test/Downloader/FileDownloaderTest.php
+++ b/tests/Composer/Test/Downloader/FileDownloaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Downloader/FossilDownloaderTest.php b/tests/Composer/Test/Downloader/FossilDownloaderTest.php
index ebe9cf75e66e..7a080c8b8d7f 100644
--- a/tests/Composer/Test/Downloader/FossilDownloaderTest.php
+++ b/tests/Composer/Test/Downloader/FossilDownloaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Downloader/GitDownloaderTest.php b/tests/Composer/Test/Downloader/GitDownloaderTest.php
index 91b90b369e42..8a65686d635f 100644
--- a/tests/Composer/Test/Downloader/GitDownloaderTest.php
+++ b/tests/Composer/Test/Downloader/GitDownloaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Downloader/HgDownloaderTest.php b/tests/Composer/Test/Downloader/HgDownloaderTest.php
index 3c5712b4cf68..45b84a1ff98f 100644
--- a/tests/Composer/Test/Downloader/HgDownloaderTest.php
+++ b/tests/Composer/Test/Downloader/HgDownloaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Downloader/PerforceDownloaderTest.php b/tests/Composer/Test/Downloader/PerforceDownloaderTest.php
index f8a8e16c6323..f814861066e5 100644
--- a/tests/Composer/Test/Downloader/PerforceDownloaderTest.php
+++ b/tests/Composer/Test/Downloader/PerforceDownloaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Downloader/XzDownloaderTest.php b/tests/Composer/Test/Downloader/XzDownloaderTest.php
index f20129bfbd0e..1f060c16a2d7 100644
--- a/tests/Composer/Test/Downloader/XzDownloaderTest.php
+++ b/tests/Composer/Test/Downloader/XzDownloaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Downloader/ZipDownloaderTest.php b/tests/Composer/Test/Downloader/ZipDownloaderTest.php
index f7a44441298c..9ba06d180498 100644
--- a/tests/Composer/Test/Downloader/ZipDownloaderTest.php
+++ b/tests/Composer/Test/Downloader/ZipDownloaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/EventDispatcher/EventDispatcherTest.php b/tests/Composer/Test/EventDispatcher/EventDispatcherTest.php
index fc57a12413f6..05ca1a272ed5 100644
--- a/tests/Composer/Test/EventDispatcher/EventDispatcherTest.php
+++ b/tests/Composer/Test/EventDispatcher/EventDispatcherTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/FactoryTest.php b/tests/Composer/Test/FactoryTest.php
index ec41827fb704..636e58c317d4 100644
--- a/tests/Composer/Test/FactoryTest.php
+++ b/tests/Composer/Test/FactoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreAllPlatformRequirementFilterTest.php b/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreAllPlatformRequirementFilterTest.php
index 1c3b79a6e0ec..97a43bf80b90 100644
--- a/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreAllPlatformRequirementFilterTest.php
+++ b/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreAllPlatformRequirementFilterTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilterTest.php b/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilterTest.php
index dd1f71d85f8e..6de438ff140b 100644
--- a/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilterTest.php
+++ b/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreListPlatformRequirementFilterTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreNothingPlatformRequirementFilterTest.php b/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreNothingPlatformRequirementFilterTest.php
index 02b6ad50ce6c..239c954c1e29 100644
--- a/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreNothingPlatformRequirementFilterTest.php
+++ b/tests/Composer/Test/Filter/PlatformRequirementFilter/IgnoreNothingPlatformRequirementFilterTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Filter/PlatformRequirementFilter/PlatformRequirementFilterFactoryTest.php b/tests/Composer/Test/Filter/PlatformRequirementFilter/PlatformRequirementFilterFactoryTest.php
index d443532e3adb..ce2055e39d8c 100644
--- a/tests/Composer/Test/Filter/PlatformRequirementFilter/PlatformRequirementFilterFactoryTest.php
+++ b/tests/Composer/Test/Filter/PlatformRequirementFilter/PlatformRequirementFilterFactoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/IO/BufferIOTest.php b/tests/Composer/Test/IO/BufferIOTest.php
index 8e86f190361b..0e2d11101d3b 100644
--- a/tests/Composer/Test/IO/BufferIOTest.php
+++ b/tests/Composer/Test/IO/BufferIOTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/IO/ConsoleIOTest.php b/tests/Composer/Test/IO/ConsoleIOTest.php
index 65995c884b9d..8a0799acf863 100644
--- a/tests/Composer/Test/IO/ConsoleIOTest.php
+++ b/tests/Composer/Test/IO/ConsoleIOTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/IO/NullIOTest.php b/tests/Composer/Test/IO/NullIOTest.php
index b2ecc84d88de..d43c891fef7e 100644
--- a/tests/Composer/Test/IO/NullIOTest.php
+++ b/tests/Composer/Test/IO/NullIOTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/InstalledVersionsTest.php b/tests/Composer/Test/InstalledVersionsTest.php
index e23e90eceae0..9e06f4c2cb3e 100644
--- a/tests/Composer/Test/InstalledVersionsTest.php
+++ b/tests/Composer/Test/InstalledVersionsTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Installer/BinaryInstallerTest.php b/tests/Composer/Test/Installer/BinaryInstallerTest.php
index 28b1f0fc0606..a7e49fe685b0 100644
--- a/tests/Composer/Test/Installer/BinaryInstallerTest.php
+++ b/tests/Composer/Test/Installer/BinaryInstallerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Installer/InstallationManagerTest.php b/tests/Composer/Test/Installer/InstallationManagerTest.php
index 91057a72ab11..5b3d4b4283ec 100644
--- a/tests/Composer/Test/Installer/InstallationManagerTest.php
+++ b/tests/Composer/Test/Installer/InstallationManagerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Installer/InstallerEventTest.php b/tests/Composer/Test/Installer/InstallerEventTest.php
index d2146f3a7f32..834f7ac7b0fd 100644
--- a/tests/Composer/Test/Installer/InstallerEventTest.php
+++ b/tests/Composer/Test/Installer/InstallerEventTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Installer/LibraryInstallerTest.php b/tests/Composer/Test/Installer/LibraryInstallerTest.php
index e14a830df83a..0139661755af 100644
--- a/tests/Composer/Test/Installer/LibraryInstallerTest.php
+++ b/tests/Composer/Test/Installer/LibraryInstallerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Installer/MetapackageInstallerTest.php b/tests/Composer/Test/Installer/MetapackageInstallerTest.php
index 0b0b2035a072..114c3f95b44d 100644
--- a/tests/Composer/Test/Installer/MetapackageInstallerTest.php
+++ b/tests/Composer/Test/Installer/MetapackageInstallerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Installer/SuggestedPackagesReporterTest.php b/tests/Composer/Test/Installer/SuggestedPackagesReporterTest.php
index 5cd693d4fa77..e7fada87bab9 100644
--- a/tests/Composer/Test/Installer/SuggestedPackagesReporterTest.php
+++ b/tests/Composer/Test/Installer/SuggestedPackagesReporterTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/InstallerTest.php b/tests/Composer/Test/InstallerTest.php
index e22264338432..1fc54dc4d4de 100644
--- a/tests/Composer/Test/InstallerTest.php
+++ b/tests/Composer/Test/InstallerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Json/ComposerSchemaTest.php b/tests/Composer/Test/Json/ComposerSchemaTest.php
index e6aea2271b7b..a458ef1a0dc2 100644
--- a/tests/Composer/Test/Json/ComposerSchemaTest.php
+++ b/tests/Composer/Test/Json/ComposerSchemaTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Json/JsonFileTest.php b/tests/Composer/Test/Json/JsonFileTest.php
index 02ede63dc074..fa393fc41459 100644
--- a/tests/Composer/Test/Json/JsonFileTest.php
+++ b/tests/Composer/Test/Json/JsonFileTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Json/JsonFormatterTest.php b/tests/Composer/Test/Json/JsonFormatterTest.php
index cd95c6fc9807..88f76dfece5d 100644
--- a/tests/Composer/Test/Json/JsonFormatterTest.php
+++ b/tests/Composer/Test/Json/JsonFormatterTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Json/JsonManipulatorTest.php b/tests/Composer/Test/Json/JsonManipulatorTest.php
index 5337511322df..0e32be3bc0cf 100644
--- a/tests/Composer/Test/Json/JsonManipulatorTest.php
+++ b/tests/Composer/Test/Json/JsonManipulatorTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Json/JsonValidationExceptionTest.php b/tests/Composer/Test/Json/JsonValidationExceptionTest.php
index 863368303b61..f11dfca8808f 100644
--- a/tests/Composer/Test/Json/JsonValidationExceptionTest.php
+++ b/tests/Composer/Test/Json/JsonValidationExceptionTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Mock/FactoryMock.php b/tests/Composer/Test/Mock/FactoryMock.php
index 17e21c83be97..6c75c3e6b6e6 100644
--- a/tests/Composer/Test/Mock/FactoryMock.php
+++ b/tests/Composer/Test/Mock/FactoryMock.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Mock/HttpDownloaderMock.php b/tests/Composer/Test/Mock/HttpDownloaderMock.php
index b919b294b020..beb12ecc8fcc 100644
--- a/tests/Composer/Test/Mock/HttpDownloaderMock.php
+++ b/tests/Composer/Test/Mock/HttpDownloaderMock.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Mock/InstallationManagerMock.php b/tests/Composer/Test/Mock/InstallationManagerMock.php
index ed4eaa873ac7..593093ded3e3 100644
--- a/tests/Composer/Test/Mock/InstallationManagerMock.php
+++ b/tests/Composer/Test/Mock/InstallationManagerMock.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Mock/InstalledFilesystemRepositoryMock.php b/tests/Composer/Test/Mock/InstalledFilesystemRepositoryMock.php
index 101005cda152..b75b5df8c0d4 100644
--- a/tests/Composer/Test/Mock/InstalledFilesystemRepositoryMock.php
+++ b/tests/Composer/Test/Mock/InstalledFilesystemRepositoryMock.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Mock/ProcessExecutorMock.php b/tests/Composer/Test/Mock/ProcessExecutorMock.php
index b3e7d176eb60..b8948e6ae721 100644
--- a/tests/Composer/Test/Mock/ProcessExecutorMock.php
+++ b/tests/Composer/Test/Mock/ProcessExecutorMock.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Mock/VersionGuesserMock.php b/tests/Composer/Test/Mock/VersionGuesserMock.php
index b634b0297f73..c8a0c95d0955 100644
--- a/tests/Composer/Test/Mock/VersionGuesserMock.php
+++ b/tests/Composer/Test/Mock/VersionGuesserMock.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Archiver/ArchivableFilesFinderTest.php b/tests/Composer/Test/Package/Archiver/ArchivableFilesFinderTest.php
index 2fb91a2b22cd..7fe88cb4196e 100644
--- a/tests/Composer/Test/Package/Archiver/ArchivableFilesFinderTest.php
+++ b/tests/Composer/Test/Package/Archiver/ArchivableFilesFinderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Archiver/ArchiveManagerTest.php b/tests/Composer/Test/Package/Archiver/ArchiveManagerTest.php
index 04f098355bdf..5a898694b0ff 100644
--- a/tests/Composer/Test/Package/Archiver/ArchiveManagerTest.php
+++ b/tests/Composer/Test/Package/Archiver/ArchiveManagerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Archiver/ArchiverTest.php b/tests/Composer/Test/Package/Archiver/ArchiverTest.php
index eecd8dff2a09..13c4ed0f7d97 100644
--- a/tests/Composer/Test/Package/Archiver/ArchiverTest.php
+++ b/tests/Composer/Test/Package/Archiver/ArchiverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Archiver/GitExcludeFilterTest.php b/tests/Composer/Test/Package/Archiver/GitExcludeFilterTest.php
index 32c255cfc544..79c57f0d0b07 100644
--- a/tests/Composer/Test/Package/Archiver/GitExcludeFilterTest.php
+++ b/tests/Composer/Test/Package/Archiver/GitExcludeFilterTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Archiver/PharArchiverTest.php b/tests/Composer/Test/Package/Archiver/PharArchiverTest.php
index 22ebb83d5e35..0ad1d4eb58c5 100644
--- a/tests/Composer/Test/Package/Archiver/PharArchiverTest.php
+++ b/tests/Composer/Test/Package/Archiver/PharArchiverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Archiver/ZipArchiverTest.php b/tests/Composer/Test/Package/Archiver/ZipArchiverTest.php
index 7e4fb7f896d9..e216fe0a6883 100644
--- a/tests/Composer/Test/Package/Archiver/ZipArchiverTest.php
+++ b/tests/Composer/Test/Package/Archiver/ZipArchiverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/BasePackageTest.php b/tests/Composer/Test/Package/BasePackageTest.php
index 90921bc7cfdf..acc8f4de37ae 100644
--- a/tests/Composer/Test/Package/BasePackageTest.php
+++ b/tests/Composer/Test/Package/BasePackageTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/CompletePackageTest.php b/tests/Composer/Test/Package/CompletePackageTest.php
index 4f57dff145e4..a1edd1560ebb 100644
--- a/tests/Composer/Test/Package/CompletePackageTest.php
+++ b/tests/Composer/Test/Package/CompletePackageTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Dumper/ArrayDumperTest.php b/tests/Composer/Test/Package/Dumper/ArrayDumperTest.php
index 8b1d5af0cd80..a4b3fc0d2c2c 100644
--- a/tests/Composer/Test/Package/Dumper/ArrayDumperTest.php
+++ b/tests/Composer/Test/Package/Dumper/ArrayDumperTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Loader/ArrayLoaderTest.php b/tests/Composer/Test/Package/Loader/ArrayLoaderTest.php
index 2324ad0c25c7..fa2a180a9dac 100644
--- a/tests/Composer/Test/Package/Loader/ArrayLoaderTest.php
+++ b/tests/Composer/Test/Package/Loader/ArrayLoaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Loader/RootPackageLoaderTest.php b/tests/Composer/Test/Package/Loader/RootPackageLoaderTest.php
index a669f669f964..7f8872fc14e4 100644
--- a/tests/Composer/Test/Package/Loader/RootPackageLoaderTest.php
+++ b/tests/Composer/Test/Package/Loader/RootPackageLoaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Loader/ValidatingArrayLoaderTest.php b/tests/Composer/Test/Package/Loader/ValidatingArrayLoaderTest.php
index a8204a76f909..fd105f7e1329 100644
--- a/tests/Composer/Test/Package/Loader/ValidatingArrayLoaderTest.php
+++ b/tests/Composer/Test/Package/Loader/ValidatingArrayLoaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/LockerTest.php b/tests/Composer/Test/Package/LockerTest.php
index d2913e36ddda..34e8be360d9f 100644
--- a/tests/Composer/Test/Package/LockerTest.php
+++ b/tests/Composer/Test/Package/LockerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/RootAliasPackageTest.php b/tests/Composer/Test/Package/RootAliasPackageTest.php
index 0a42fd31dd8b..c871cd1f5191 100644
--- a/tests/Composer/Test/Package/RootAliasPackageTest.php
+++ b/tests/Composer/Test/Package/RootAliasPackageTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Version/VersionGuesserTest.php b/tests/Composer/Test/Package/Version/VersionGuesserTest.php
index 4ec717681f26..e5076862a512 100644
--- a/tests/Composer/Test/Package/Version/VersionGuesserTest.php
+++ b/tests/Composer/Test/Package/Version/VersionGuesserTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Version/VersionParserTest.php b/tests/Composer/Test/Package/Version/VersionParserTest.php
index 2f120a7f8bfe..5f2109e8ead2 100644
--- a/tests/Composer/Test/Package/Version/VersionParserTest.php
+++ b/tests/Composer/Test/Package/Version/VersionParserTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Package/Version/VersionSelectorTest.php b/tests/Composer/Test/Package/Version/VersionSelectorTest.php
index 4ff61029cc17..1cf08155e929 100644
--- a/tests/Composer/Test/Package/Version/VersionSelectorTest.php
+++ b/tests/Composer/Test/Package/Version/VersionSelectorTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Platform/HhvmDetectorTest.php b/tests/Composer/Test/Platform/HhvmDetectorTest.php
index eaf93c9827fa..c39395ff1210 100644
--- a/tests/Composer/Test/Platform/HhvmDetectorTest.php
+++ b/tests/Composer/Test/Platform/HhvmDetectorTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Platform/VersionTest.php b/tests/Composer/Test/Platform/VersionTest.php
index 4ae361bb554c..00497ef94107 100644
--- a/tests/Composer/Test/Platform/VersionTest.php
+++ b/tests/Composer/Test/Platform/VersionTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Plugin/Mock/Capability.php b/tests/Composer/Test/Plugin/Mock/Capability.php
index a9dd4accb6b6..f7cb608b493b 100644
--- a/tests/Composer/Test/Plugin/Mock/Capability.php
+++ b/tests/Composer/Test/Plugin/Mock/Capability.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Plugin/Mock/CapablePluginInterface.php b/tests/Composer/Test/Plugin/Mock/CapablePluginInterface.php
index 5e8d88c31db3..9f84554aaeed 100644
--- a/tests/Composer/Test/Plugin/Mock/CapablePluginInterface.php
+++ b/tests/Composer/Test/Plugin/Mock/CapablePluginInterface.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Plugin/PluginInstallerTest.php b/tests/Composer/Test/Plugin/PluginInstallerTest.php
index 32b2afc36017..99392e0845ea 100644
--- a/tests/Composer/Test/Plugin/PluginInstallerTest.php
+++ b/tests/Composer/Test/Plugin/PluginInstallerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Question/StrictConfirmationQuestionTest.php b/tests/Composer/Test/Question/StrictConfirmationQuestionTest.php
index 2c21d869dd6c..c85f38cef754 100644
--- a/tests/Composer/Test/Question/StrictConfirmationQuestionTest.php
+++ b/tests/Composer/Test/Question/StrictConfirmationQuestionTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/ArrayRepositoryTest.php b/tests/Composer/Test/Repository/ArrayRepositoryTest.php
index f2261eac2b9a..04c45959f1f3 100644
--- a/tests/Composer/Test/Repository/ArrayRepositoryTest.php
+++ b/tests/Composer/Test/Repository/ArrayRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/ArtifactRepositoryTest.php b/tests/Composer/Test/Repository/ArtifactRepositoryTest.php
index ee44153a322d..c038dfc2facb 100644
--- a/tests/Composer/Test/Repository/ArtifactRepositoryTest.php
+++ b/tests/Composer/Test/Repository/ArtifactRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/ComposerRepositoryTest.php b/tests/Composer/Test/Repository/ComposerRepositoryTest.php
index fcfc2fa4cbee..854a388ec37a 100644
--- a/tests/Composer/Test/Repository/ComposerRepositoryTest.php
+++ b/tests/Composer/Test/Repository/ComposerRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/CompositeRepositoryTest.php b/tests/Composer/Test/Repository/CompositeRepositoryTest.php
index edf914e73ef7..ca123a3b3e96 100644
--- a/tests/Composer/Test/Repository/CompositeRepositoryTest.php
+++ b/tests/Composer/Test/Repository/CompositeRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/FilesystemRepositoryTest.php b/tests/Composer/Test/Repository/FilesystemRepositoryTest.php
index ad0466191dc2..e16938334777 100644
--- a/tests/Composer/Test/Repository/FilesystemRepositoryTest.php
+++ b/tests/Composer/Test/Repository/FilesystemRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/FilterRepositoryTest.php b/tests/Composer/Test/Repository/FilterRepositoryTest.php
index eb96d876f64b..7fa24236a20d 100644
--- a/tests/Composer/Test/Repository/FilterRepositoryTest.php
+++ b/tests/Composer/Test/Repository/FilterRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/InstalledRepositoryTest.php b/tests/Composer/Test/Repository/InstalledRepositoryTest.php
index c4f32a1a5eb3..e9efc04ffda4 100644
--- a/tests/Composer/Test/Repository/InstalledRepositoryTest.php
+++ b/tests/Composer/Test/Repository/InstalledRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/PathRepositoryTest.php b/tests/Composer/Test/Repository/PathRepositoryTest.php
index 5d688878789a..b82837d93207 100644
--- a/tests/Composer/Test/Repository/PathRepositoryTest.php
+++ b/tests/Composer/Test/Repository/PathRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/PlatformRepositoryTest.php b/tests/Composer/Test/Repository/PlatformRepositoryTest.php
index 18c2a68d8795..0b672729b03a 100644
--- a/tests/Composer/Test/Repository/PlatformRepositoryTest.php
+++ b/tests/Composer/Test/Repository/PlatformRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/RepositoryFactoryTest.php b/tests/Composer/Test/Repository/RepositoryFactoryTest.php
index 3928d02885ea..beb8be4832d8 100644
--- a/tests/Composer/Test/Repository/RepositoryFactoryTest.php
+++ b/tests/Composer/Test/Repository/RepositoryFactoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/RepositoryManagerTest.php b/tests/Composer/Test/Repository/RepositoryManagerTest.php
index fcf826e14478..e5b4c84da338 100644
--- a/tests/Composer/Test/Repository/RepositoryManagerTest.php
+++ b/tests/Composer/Test/Repository/RepositoryManagerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/Vcs/FossilDriverTest.php b/tests/Composer/Test/Repository/Vcs/FossilDriverTest.php
index 1857cf262ae6..f43e8c02e8b8 100644
--- a/tests/Composer/Test/Repository/Vcs/FossilDriverTest.php
+++ b/tests/Composer/Test/Repository/Vcs/FossilDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/Vcs/GitBitbucketDriverTest.php b/tests/Composer/Test/Repository/Vcs/GitBitbucketDriverTest.php
index d616e3798883..7a5d3065451a 100644
--- a/tests/Composer/Test/Repository/Vcs/GitBitbucketDriverTest.php
+++ b/tests/Composer/Test/Repository/Vcs/GitBitbucketDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/Vcs/GitHubDriverTest.php b/tests/Composer/Test/Repository/Vcs/GitHubDriverTest.php
index 005f0c8172cf..bcacb53a6e17 100644
--- a/tests/Composer/Test/Repository/Vcs/GitHubDriverTest.php
+++ b/tests/Composer/Test/Repository/Vcs/GitHubDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/Vcs/GitLabDriverTest.php b/tests/Composer/Test/Repository/Vcs/GitLabDriverTest.php
index 368655ec269f..1aeeb23d457b 100644
--- a/tests/Composer/Test/Repository/Vcs/GitLabDriverTest.php
+++ b/tests/Composer/Test/Repository/Vcs/GitLabDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/Vcs/HgDriverTest.php b/tests/Composer/Test/Repository/Vcs/HgDriverTest.php
index 0d6948415c9d..58cac0c1646e 100644
--- a/tests/Composer/Test/Repository/Vcs/HgDriverTest.php
+++ b/tests/Composer/Test/Repository/Vcs/HgDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/Vcs/PerforceDriverTest.php b/tests/Composer/Test/Repository/Vcs/PerforceDriverTest.php
index fda883a43825..98ee5f3eacc5 100644
--- a/tests/Composer/Test/Repository/Vcs/PerforceDriverTest.php
+++ b/tests/Composer/Test/Repository/Vcs/PerforceDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/Vcs/SvnDriverTest.php b/tests/Composer/Test/Repository/Vcs/SvnDriverTest.php
index e18f64af3e8a..d6310ebf5a8a 100644
--- a/tests/Composer/Test/Repository/Vcs/SvnDriverTest.php
+++ b/tests/Composer/Test/Repository/Vcs/SvnDriverTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Repository/VcsRepositoryTest.php b/tests/Composer/Test/Repository/VcsRepositoryTest.php
index a4e1753970ae..ac5884584123 100644
--- a/tests/Composer/Test/Repository/VcsRepositoryTest.php
+++ b/tests/Composer/Test/Repository/VcsRepositoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Script/EventTest.php b/tests/Composer/Test/Script/EventTest.php
index 724d0e886889..102d6e5f5e80 100644
--- a/tests/Composer/Test/Script/EventTest.php
+++ b/tests/Composer/Test/Script/EventTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/TestCase.php b/tests/Composer/Test/TestCase.php
index 0e61bb87ab29..a26dbfb6e6cf 100644
--- a/tests/Composer/Test/TestCase.php
+++ b/tests/Composer/Test/TestCase.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/AuthHelperTest.php b/tests/Composer/Test/Util/AuthHelperTest.php
index b179688e2a4e..f38b375aa7df 100644
--- a/tests/Composer/Test/Util/AuthHelperTest.php
+++ b/tests/Composer/Test/Util/AuthHelperTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/BitbucketTest.php b/tests/Composer/Test/Util/BitbucketTest.php
index 525e90456e8b..5d1b83c25246 100644
--- a/tests/Composer/Test/Util/BitbucketTest.php
+++ b/tests/Composer/Test/Util/BitbucketTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/ConfigValidatorTest.php b/tests/Composer/Test/Util/ConfigValidatorTest.php
index c755ea6e5b50..cdbb8785109f 100644
--- a/tests/Composer/Test/Util/ConfigValidatorTest.php
+++ b/tests/Composer/Test/Util/ConfigValidatorTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/ErrorHandlerTest.php b/tests/Composer/Test/Util/ErrorHandlerTest.php
index 4def526a4cb3..7d48d8963ed2 100644
--- a/tests/Composer/Test/Util/ErrorHandlerTest.php
+++ b/tests/Composer/Test/Util/ErrorHandlerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/FilesystemTest.php b/tests/Composer/Test/Util/FilesystemTest.php
index 20298d534685..e40e532674eb 100644
--- a/tests/Composer/Test/Util/FilesystemTest.php
+++ b/tests/Composer/Test/Util/FilesystemTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/GitHubTest.php b/tests/Composer/Test/Util/GitHubTest.php
index a4151f489167..72b2e1c2cefa 100644
--- a/tests/Composer/Test/Util/GitHubTest.php
+++ b/tests/Composer/Test/Util/GitHubTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/GitLabTest.php b/tests/Composer/Test/Util/GitLabTest.php
index 61bc35c7249a..d1f44d946469 100644
--- a/tests/Composer/Test/Util/GitLabTest.php
+++ b/tests/Composer/Test/Util/GitLabTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/GitTest.php b/tests/Composer/Test/Util/GitTest.php
index c91a34248683..41602aa0b8b8 100644
--- a/tests/Composer/Test/Util/GitTest.php
+++ b/tests/Composer/Test/Util/GitTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/Http/ProxyHelperTest.php b/tests/Composer/Test/Util/Http/ProxyHelperTest.php
index 4de4c654ae16..c70dd746d83e 100644
--- a/tests/Composer/Test/Util/Http/ProxyHelperTest.php
+++ b/tests/Composer/Test/Util/Http/ProxyHelperTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/Http/ProxyManagerTest.php b/tests/Composer/Test/Util/Http/ProxyManagerTest.php
index ea5eb78f72e7..ebdc4d290d86 100644
--- a/tests/Composer/Test/Util/Http/ProxyManagerTest.php
+++ b/tests/Composer/Test/Util/Http/ProxyManagerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/Http/RequestProxyTest.php b/tests/Composer/Test/Util/Http/RequestProxyTest.php
index 474c6857e152..2073d70bf75c 100644
--- a/tests/Composer/Test/Util/Http/RequestProxyTest.php
+++ b/tests/Composer/Test/Util/Http/RequestProxyTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/HttpDownloaderTest.php b/tests/Composer/Test/Util/HttpDownloaderTest.php
index fe49c1ca5e0e..26e77876440d 100644
--- a/tests/Composer/Test/Util/HttpDownloaderTest.php
+++ b/tests/Composer/Test/Util/HttpDownloaderTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/IniHelperTest.php b/tests/Composer/Test/Util/IniHelperTest.php
index a3e8bc8e65ef..753efcee0462 100644
--- a/tests/Composer/Test/Util/IniHelperTest.php
+++ b/tests/Composer/Test/Util/IniHelperTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/MetadataMinifierTest.php b/tests/Composer/Test/Util/MetadataMinifierTest.php
index 44e28c9b2ac7..99f61c0b6fe6 100644
--- a/tests/Composer/Test/Util/MetadataMinifierTest.php
+++ b/tests/Composer/Test/Util/MetadataMinifierTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/NoProxyPatternTest.php b/tests/Composer/Test/Util/NoProxyPatternTest.php
index 7b00da615361..559875375384 100644
--- a/tests/Composer/Test/Util/NoProxyPatternTest.php
+++ b/tests/Composer/Test/Util/NoProxyPatternTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/PackageSorterTest.php b/tests/Composer/Test/Util/PackageSorterTest.php
index 63734925fb68..67cdd13bb549 100644
--- a/tests/Composer/Test/Util/PackageSorterTest.php
+++ b/tests/Composer/Test/Util/PackageSorterTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/PerforceTest.php b/tests/Composer/Test/Util/PerforceTest.php
index 7b524337f187..44617633abd4 100644
--- a/tests/Composer/Test/Util/PerforceTest.php
+++ b/tests/Composer/Test/Util/PerforceTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/PlatformTest.php b/tests/Composer/Test/Util/PlatformTest.php
index f05d3a736c96..b6be7b8974eb 100644
--- a/tests/Composer/Test/Util/PlatformTest.php
+++ b/tests/Composer/Test/Util/PlatformTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/ProcessExecutorTest.php b/tests/Composer/Test/Util/ProcessExecutorTest.php
index c1aac5ad7278..4e57e206fddd 100644
--- a/tests/Composer/Test/Util/ProcessExecutorTest.php
+++ b/tests/Composer/Test/Util/ProcessExecutorTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/RemoteFilesystemTest.php b/tests/Composer/Test/Util/RemoteFilesystemTest.php
index eebe8f90001c..4fc7c745409f 100644
--- a/tests/Composer/Test/Util/RemoteFilesystemTest.php
+++ b/tests/Composer/Test/Util/RemoteFilesystemTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/SilencerTest.php b/tests/Composer/Test/Util/SilencerTest.php
index 58a81eb92105..0c9ad5777a24 100644
--- a/tests/Composer/Test/Util/SilencerTest.php
+++ b/tests/Composer/Test/Util/SilencerTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/StreamContextFactoryTest.php b/tests/Composer/Test/Util/StreamContextFactoryTest.php
index ca78f1c4c1f9..e16d9ad79061 100644
--- a/tests/Composer/Test/Util/StreamContextFactoryTest.php
+++ b/tests/Composer/Test/Util/StreamContextFactoryTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/SvnTest.php b/tests/Composer/Test/Util/SvnTest.php
index b6d6062f936e..4f5d2eaec116 100644
--- a/tests/Composer/Test/Util/SvnTest.php
+++ b/tests/Composer/Test/Util/SvnTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/TarTest.php b/tests/Composer/Test/Util/TarTest.php
index b0e6978197a4..86c7564cd321 100644
--- a/tests/Composer/Test/Util/TarTest.php
+++ b/tests/Composer/Test/Util/TarTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/TlsHelperTest.php b/tests/Composer/Test/Util/TlsHelperTest.php
index c6f1514f0cae..b2692d473f58 100644
--- a/tests/Composer/Test/Util/TlsHelperTest.php
+++ b/tests/Composer/Test/Util/TlsHelperTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/UrlTest.php b/tests/Composer/Test/Util/UrlTest.php
index 3a8b084d5444..1d26967e2ae0 100644
--- a/tests/Composer/Test/Util/UrlTest.php
+++ b/tests/Composer/Test/Util/UrlTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/Composer/Test/Util/ZipTest.php b/tests/Composer/Test/Util/ZipTest.php
index fa92fd897672..0af7ea89acd4 100644
--- a/tests/Composer/Test/Util/ZipTest.php
+++ b/tests/Composer/Test/Util/ZipTest.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index a35126cff604..19279f406b98 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.
diff --git a/tests/console-application.php b/tests/console-application.php
index 4ee45c8eef7a..9a8b9750a1fa 100644
--- a/tests/console-application.php
+++ b/tests/console-application.php
@@ -1,4 +1,4 @@
-<?php
+<?php declare(strict_types=1);
 
 /*
  * This file is part of Composer.