PHP variable function usage analysis

PHP supports the concept of variable functions. This means that if a variable name has parentheses after it, PHP will look for a function with the same name as the variable's value and try to execute it. Variable functions can be used to implement some purposes including callback functions and function tables.

Variable functions cannot be used in language structures, such as echo(), print(), unset(), isset(), empty(), include() , require() and similar statements . You need to use your own wrapper function to use these structures as variable functions.
Example #1 Variable function example

<?php
function  foo () {
    echo  "In foo()<br />/n" ;
}
function  bar ( $arg  =  &#39;&#39; ) {
    echo  "In bar(); argument was &#39; $arg &#39;.<br />/n" ;
}
// 使用 echo 的包装函数
function  echoit ( $string )
{
    echo  $string ;
}
$func  =  &#39;foo&#39; ;
$func ();         // This calls foo()
$func  =  &#39;bar&#39; ;
$func ( &#39;test&#39; );   // This calls bar()
$func  =  &#39;echoit&#39; ;
$func ( &#39;test&#39; );   // This calls echoit()
?>

You can also use the characteristics of the variable function to call the method of an object.

Example #2 Variable method example

<?php
class  Foo
{
    function  Variable ()
    {
         $name  =  &#39;Bar&#39; ;
         $this -> $name ();  // This calls the Bar() method
     }
    function  Bar ()
    {
        echo  "This is Bar" ;
    }
}
$foo  = new  Foo ();
$funcname  =  "Variable" ;
$foo -> $funcname ();    // This calls $foo->Variable()
?>

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