PHP Variable function usage analysis

PHP supports the concept of mutable functions. This means that if aVariable name with parentheses, PHP looks for a function with the same name as the value of the variable, and tries to execute it. Variable functions can be used to implement includingcallback function , a function table, for some purposes.

Variable functions cannot be used for language structures such as echo (), print (), unset (), Isset (), empty (), include (), require (), and similar statements . These structures need to be used as variable functions using their own wrapper functions.
Example #1 Variable Function example

<?phpfunction  foo () {    echo  "in foo () <br/>/n";} function  Bar ($arg  = "  ) {    echo" in  bar (); argument is ' $arg '. <br/>/n ";} Use Echo's wrapper function  Echoit ($string) {    echo  $string;} $func  =  ' foo '; $func ();         This calls foo () $func  =  ' bar '; $func (' Test ');   This calls bar () $func  =  ' Echoit '; $func (' Test ');   This calls Echoit ()?>

You can also use the properties of a mutable function to invoke a method of an object.

Example #2 Variable Method Example

<?phpclass  foo{    function  Variable ()    {         $name  =  ' Bar ';         $this $name ();  This calls the bar () method     }    function  Bar ()    {        echo  ' this is Bar ';    }} $foo  = new  foo (); $funcname  =  "Variable"; $foo-$funcname ();    This calls $foo->variable ()?>