Php-namespace keywords and __namespace__ constants

PHP supports two abstract methods of accessing the inner elements of the current namespace, __namespace__ Magic constants and NAMESPACE keywords.

The value of the constant __namespace__ is a string containing the name of the current namespace. In the global, not included in any namespace code, it contains an empty string.

Example #1 __namespace__ example, the code in the namespace

<?php    namespace MyProject;    Echo ' "', __namespace__, '"; Output "MyProject"?>

Example #2 __namespace__ example, Global code

<?php    Echo ' "', __namespace__, '"; Output ""?>

Constant __namespace__ is useful when creating names dynamically, for example:

Example #3 Create names dynamically using __namespace__

<?php    namespace MyProject;    function Get ($classname)    {        $a = __namespace__. '\\' . $classname;        return new $a;    }? >

The keyword namespace can be used to explicitly access elements in the current namespace or in a sub-namespace. It is equivalent to the self operator in the class.

Example #4 namespace operator, code in the namespace

<?php    namespace MyProject;    Use Blah\blah as mine; Namespace aliases (refer to: Using namespace aliases and imports)    blah\mine ();//Call Function Blah\blah\mine ()    namespace\blah\mine ();//Call Function Myproject\blah \mine ()    namespace\func ();//Call Function Myproject\func ()    namespace\sub\func ();//Call Function Myproject\sub\func ()    Namespace\cname::method (); Call the static method of the class Myproject\cname "method"     $a = new Namespace\sub\cname ();//Instantiate the Class Myproject\sub\cname object     $b = Namespace\constant; Assigns the value of the constant myproject\constant to the $b?>

Example #5 namespace operator, global code

<?php Namespace\func (); Call function func ()   namespace\sub\func ();//Call Function Sub\func ()   namespace\cname::method ();//Call the static method of the class CNAME c11/> $a = new Namespace\sub\cname (); Instantiate the Sub\cname class object   $b = namespace\constant;//assigns the value of the constant CONSTANT to the $b?>

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