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namespace keyword and __NAMESPACE__ constant
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.
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namespace MyProject;
echo '"', __NAMESPACE__, '"'; // outputs "MyProject"
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echo '"', __NAMESPACE__, '"'; // outputs ""
The __NAMESPACE__ constant is useful for dynamically constructing names, for instance:
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namespace 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.
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namespace MyProject;
use blah\blah as mine; // see "Using namespaces: importing/aliasing"
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
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namespace\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