Name resolution rules

(PHP 5 >= 5.3.0, PHP 7)

For the purposes of these resolution rules, here are some important definitions:

Namespace name definitions Unqualified name

This is an identifier without a namespace separator, such as Foo

Qualified name

This is an identifier with a namespace separator, such as Foo\Bar

Fully qualified name

This is an identifier with a namespace separator that begins with a namespace separator, such as \Foo\Bar. The namespace \Foo is also a fully qualified name.

Relative name

This is an identifier starting with namespace, such as namespace\Foo\Bar.

Names are resolved following these resolution rules:

Fully qualified names always resolve to the name without leading namespace separator. For instance \A\B resolves to A\B.

Example #1 Name resolutions illustrated

<?php
namespace A;
use B\D, C\E as F;

// function calls

foo(      // first tries to call "foo" defined in namespace "A"
            // then calls global function "foo"

\foo(     // calls function "foo" defined in global scope

my\foo(   // calls function "foo" defined in namespace "A\my"

F(        // first tries to call "F" defined in namespace "A"
            // then calls global function "F"

// class references

new B(    // creates object of class "B" defined in namespace "A"
            // if not found, it tries to autoload class "A\B"

new D(    // using import rules, creates object of class "D" defined in namespace "B"
            // if not found, it tries to autoload class "B\D"

new F(    // using import rules, creates object of class "E" defined in namespace "C"
            // if not found, it tries to autoload class "C\E"

new \B(   // creates object of class "B" defined in global scope
            // if not found, it tries to autoload class "B"

new \D(   // creates object of class "D" defined in global scope
            // if not found, it tries to autoload class "D"

new \F(   // creates object of class "F" defined in global scope
            // if not found, it tries to autoload class "F"

// static methods/namespace functions from another namespace

B\foo(    // calls function "foo" from namespace "A\B"

B::foo(   // calls method "foo" of class "B" defined in namespace "A"
            // if class "A\B" not found, it tries to autoload class "A\B"

D::foo(   // using import rules, calls method "foo" of class "D" defined in namespace "B"
            // if class "B\D" not found, it tries to autoload class "B\D"

\B\foo(   // calls function "foo" from namespace "B"

\B::foo(  // calls method "foo" of class "B" from global scope
            // if class "B" not found, it tries to autoload class "B"

// static methods/namespace functions of current namespace

A\B::foo(   // calls method "foo" of class "B" from namespace "A\A"
              // if class "A\A\B" not found, it tries to autoload class "A\A\B"

\A\B::foo(  // calls method "foo" of class "B" from namespace "A"
              // if class "A\B" not found, it tries to autoload class "A\B"
?>

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