PHP魔术常量

下面来看看一个上面的每个魔法常量的例子。

文件名：magic.php

";// print Your current line number i.e;3  
    echo "Example for __FILE__";  
    echo __FILE__ . "

";//print full path of file with .php extension  
    echo "Example for __DIR__";  
    echo __DIR__ . "

";//print full path of directory where script will be placed  
    echo dirname(__FILE__) . "

"; //its output is equivalent to above one.  
    echo "Example for __FUNCTION__";  
    //Using magic constant inside function.  
    function cash(){  
 echo 'the function name is '. __FUNCTION__ . "

";//the function name is cash.  
    }  

    cash();  

    //Using magic constant outside function gives the blank output.  
    function test_function(){  
 echo 'HYIIII';  
    }  

    test_function();  
    echo  __FUNCTION__ . "

";//gives the blank output.  

    echo "Example for __CLASS__";  
    class abc  
    {  
 public function __construct() {  
     ;  
 }  

 function abc_method(){  
 echo __CLASS__ . "

";//print name of the class abc.  
 }  
    }  
    $t = new abc;  
    $t->abc_method(); 

    class first{  
 function test_first(){  
     echo __CLASS__;//will always print parent class which is first here.  
 }  
    }  

    class second extends first  
    {  
 public function __construct() {  
     ;  
 }  
    }  
    $t = new second;  
    $t->test_first();  

    echo "Example for __TRAIT__";  
    trait created_trait{  
 function abc(){  
     echo __TRAIT__;//will print name of the trait created_trait  
 }  
    }  

    class anew{  
 use created_trait;  
    }  
    $a = new anew;  
    $a->abc();  
    echo "Example for __METHOD__";  

    class meth{  
 public function __construct() {  
     echo __METHOD__ . "

";//print meth::__construct  
 }  
 public function meth_fun(){  
     echo __METHOD__;//print meth::meth_fun  
 }  
    }  
    $a = new meth;  
    $a->meth_fun();  

    echo "Example for __NAMESPACE__";  
    class name{  
 public function __construct() {  
     echo 'This line will be printed on calling namespace';  
 }  
    }  
    $clas_name= __NAMESPACE__ .'name';  
    $a = new $clas_name;  

?>