Avoid too much overhead in layout_init (protocolbuffers#6716)

* Avoid initializing primitive fields in layout_init

* Avoid initializing string/bytes/message fields in layout_init

* Lazily create map when needed

* Lazily create repeated fields

* Change layout_init to only do memcpy

* Fix test for php-7.0

* Fix conformance test where default value of string/message map is not encoded

* Fix test for zts

* Clean up

* Fix comments

.gitignore

@@ -139,6 +139,8 @@ composer.lock
 php/tests/generated/
 php/tests/old_protoc
 php/tests/protobuf/
+php/tests/core
+php/tests/vgcore*
 php/ext/google/protobuf/.libs/
 php/ext/google/protobuf/Makefile.fragments
 php/ext/google/protobuf/Makefile.global

php/ext/google/protobuf/array.c

@@ -259,6 +259,19 @@ void repeated_field_push_native(RepeatedField *intern, void *value) {
   }
 }
 
+void repeated_field_ensure_created(
+    const upb_fielddef *field,
+    CACHED_VALUE *repeated_field PHP_PROTO_TSRMLS_DC) {
+  if (ZVAL_IS_NULL(CACHED_PTR_TO_ZVAL_PTR(repeated_field))) {
+    zval_ptr_dtor(repeated_field);
+#if PHP_MAJOR_VERSION < 7
+    MAKE_STD_ZVAL(CACHED_PTR_TO_ZVAL_PTR(repeated_field));
+#endif
+    repeated_field_create_with_field(repeated_field_type, field,
+                                     repeated_field PHP_PROTO_TSRMLS_CC);
+  }
+}
+
 void repeated_field_create_with_field(
     zend_class_entry *ce, const upb_fielddef *field,
     CACHED_VALUE *repeated_field PHP_PROTO_TSRMLS_DC) {