Name resolution rules
(PHP 5 >= 5.3.0, PHP 7, PHP 8)
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\Foois also a fully qualified name. - Relative name
-
This is an identifier starting with
namespace, such asnamespace\Foo\Bar.
Names are resolved following these resolution rules:
-
Fully qualified names always resolve to the name without leading namespace separator.
For instance
\A\Bresolves toA\B. -
Relative names always resolve to the name with
namespacereplaced by the current namespace. If the name occurs in the global namespace, thenamespace\prefix is stripped. For examplenamespace\Ainside namespaceX\Yresolves toX\Y\A. The same name inside the global namespace resolves toA. -
For qualified names the first segment of the name is translated according to the current
class/namespace import table. For example, if the namespace
A\B\Cis imported asC, the nameC\D\Eis translated toA\B\C\D\E. -
For qualified names, if no import rule applies, the current namespace is prepended to the
name. For example, the name
C\D\Einside namespaceA\B, resolves toA\B\C\D\E. -
For unqualified names, the name is translated according to the current import table for the
respective symbol type. This means that class-like names are translated according to the
class/namespace import table, function names according to the function import table and
constants according to the constant import table. For example, after
use A\B\C;a usage such asnew C()resolves to the nameA\B\C(). Similarly, afteruse function A\B\fn;a usage such asfn()resolves to the nameA\B\fn. -
For unqualified names, if no import rule applies and the name refers to a class-like symbol,
the current namespace is prepended. For example
new C()inside namespaceA\Bresolves to nameA\B\C. -
For unqualified names, if no import rule applies and the name refers to a function or constant
and the code is outside the global namespace, the name is resolved at runtime.
Assuming the code is in namespace
A\B, here is how a call to functionfoo()is resolved:-
It looks for a function from the current namespace:
A\B\foo(). -
It tries to find and call the global function
foo().
-
It looks for a function from the current namespace:
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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