Php/docs/language.namespaces.nsconstants
namespace keyword and __NAMESPACE__ constant
(PHP 5 >= 5.3.0, PHP 7, PHP 8)
PHP supports two ways of abstractly accessing elements within the current namespace,
the __NAMESPACE__ magic constant, and the namespace
keyword.
The value of __NAMESPACE__ is a string that contains the current
namespace name. In global, un-namespaced code, it contains an empty string.
Example #1 __NAMESPACE__ example, namespaced code
<?phpnamespace MyProject;echo '"', __NAMESPACE__, '"'; // outputs "MyProject"?>
Example #2 __NAMESPACE__ example, global code
<?phpecho '"', __NAMESPACE__, '"'; // outputs ""?>
The __NAMESPACE__ constant is useful for dynamically constructing
names, for instance:
Example #3 using __NAMESPACE__ for dynamic name construction
<?phpnamespace MyProject;function get($classname){ $a = __NAMESPACE__ . '\\' . $classname; return new $a;}?>
The namespace keyword can be used to explicitly request
an element from the current namespace or a sub-namespace. It is the namespace
equivalent of the self operator for classes.
Example #4 the namespace operator, inside a namespace
<?phpnamespace MyProject;use blah\blah as mine; // see "Using namespaces: Aliasing/Importing"blah\mine(); // calls function MyProject\blah\mine()namespace\blah\mine(); // calls function MyProject\blah\mine()namespace\func(); // calls function MyProject\func()namespace\sub\func(); // calls function MyProject\sub\func()namespace\cname::method(); // calls static method "method" of class MyProject\cname$a = new namespace\sub\cname(); // instantiates object of class MyProject\sub\cname$b = namespace\CONSTANT; // assigns value of constant MyProject\CONSTANT to $b?>
Example #5 the namespace operator, in global code
<?phpnamespace\func(); // calls function func()namespace\sub\func(); // calls function sub\func()namespace\cname::method(); // calls static method "method" of class cname$a = new namespace\sub\cname(); // instantiates object of class sub\cname$b = namespace\CONSTANT; // assigns value of constant CONSTANT to $b?>
