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PHP namespace keyword and __NAMESPACE__ constant
Introduction
In PHP, namespace keyword is used to define a namespace. It is also used as an operator to request access to certain element in current namespace. The __NAMESPACE__ constant returns name of current namespace
__NAMESPACE Constant
From a named namespace, __NAMESPACE__ returns its name, for global and un-named namespace it returns empty striing
Example
#test1.php <?php echo "name of global namespace : " . __NAMESPACE__ . "
"; ?>
Output
An empty string is returned
name of global namespace :
For named namespace, its name is returned
Example
<?php namespace myspace; echo "name of current namespace : " . __NAMESPACE__ . "
"; ?>
Output
name of current namespace : myspace
Dynamic name construction
__NAMESPACE__ is useful for constructing name dynamically
Example
<?php
namespace MyProject;
class myclass {
function hello(){echo "hello world";}
};
$cls="myclass";
function get($cls){
$a = __NAMESPACE__ . '\' . $cls;
return new $a;
}
get($cls)->hello();
?>Output
Above code shows following output
hello World
namespace operator
The namespace keyword can be used as equivalent of the self operator for classes to explicitly request an element from the current namespace or a sub-namespace.
Example
<?php
namespace Myspace;
class myclass {
function hello(){echo "hello Myspace";}
}
$a = new namespace\myclass();
$a->hello();
?>Output
Above code shows following output
hello Myspace
From global namespace, namespace operator refers to function/class in current namespace which is global namespace
Example
<?php
class myclass {
function hello(){echo "hello global space";}
}
$a = new namespace\myclass();
$a->hello();
?>Output
Above code shows following output
hello global space
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