Name_resolution.markdown

Name resolution

Since the introduction of namespaces in PHP 5.3, literal names in PHP code are subject to a relatively complex name resolution process, which is based on the current namespace, the current import table state, as well the type of the referenced symbol. PHP-Parser implements name resolution and related functionality, both as reusable logic (NameContext), as well as a node visitor (NameResolver) based on it.

The NameResolver visitor

The NameResolver visitor can (and for nearly all uses of the AST, is) be applied to resolve names to their fully-qualified form, to the degree that this is possible.

$nameResolver = new PhpParser\NodeVisitor\NameResolver;
$nodeTraverser = new PhpParser\NodeTraverser;
$nodeTraverser->addVisitor($nameResolver);

// Resolve names
$stmts = $nodeTraverser->traverse($stmts);

In the default configuration, the name resolver will perform three actions:

• Declarations of functions, classes, interfaces, traits and global constants will have a namespacedName property added, which contains the function/class/etc name including the namespace prefix. For historic reasons this is a property rather than an attribute.
• Names will be replaced by fully qualified resolved names, which are instances of Node\Name\FullyQualified.
• Unqualified function and constant names inside a namespace cannot be statically resolved. Inside a namespace Foo, a call to strlen() may either refer to the namespaced \Foo\strlen(), or the global \strlen(). Because PHP-Parser does not have the necessary context to decide this, such names are left unresolved. Additionally a namespacedName attribute is added to the name node.

The name resolver accepts an option array as the second argument, with the following default values:

$nameResolver = new PhpParser\NodeVisitor\NameResolver(null, [
    'preserveOriginalNames' => false,
    'replaceNodes' => true,
]);

If the preserveOriginalNames option is enabled, then the resolved (fully qualified) name will have an originalName attribute, which contains the unresolved name.

If the replaceNodes option is disabled, then names will no longer be resolved in-place. Instead a resolvedName attribute will be added to each name, which contains the resolved (fully qualified) name. Once again, if an unqualified function or constant name cannot be resolved, then the resolvedName attribute will not be present, and instead a namespacedName attribute is added.

The replaceNodes attribute is useful if you wish to perform modifications on the AST, as you probably do not wish the resoluting code to have fully resolved names as a side-effect.

The NameContext

The actual name resolution logic is implemented in the NameContext class, which has the following public API:

class NameContext {
    public function __construct(ErrorHandler $errorHandler);
    public function startNamespace(Name $namespace = null);
    public function addAlias(Name $name, string $aliasName, int $type, array $errorAttrs = []);

    public function getNamespace();
    public function getResolvedName(Name $name, int $type);
    public function getResolvedClassName(Name $name) : Name;
    public function getPossibleNames(string $name, int $type) : array;
    public function getShortName(string $name, int $type) : Name;
}

The $type parameters accept on of the Stmt\Use_::TYPE_* constants, which represent the three basic symbol types in PHP (functions, constants and everything else).

Next to name resolution, the NameContext also supports the reverse operation of finding a short representation of a name given the current name resolution environment.

The name context is intended to be used for name resolution operations outside the AST itself, such as class names inside doc comments. A visitor running in parallel with the name resolver can access the name context using $nameResolver->getNameContext(). Alternatively a visitor can use an independent context and explicitly feed Namespace and Use nodes to it.