class_exists
(PHP  4 , PHP  5 )

class_exists -- Checks if the class has been defined
Description
bool class_exists ( string class_name [, bool autoload] )


This function checks if the given class have been defined. 

Parameters


class_name
The class name 

autoload
Whether to call __autoload or not by default 


Return Values
Returns TRUE if class_name is a defined class, FALSE otherwise. 

ChangeLog


Version Description 
 5 . 0 . 0  The autoload was added.  



Examples
Example  1 . class_exists() example

<?php
// Check the class exists before trying to use it
if (class_exists('MyClass')) {
    $myclass = new MyClass();
}

?>  
 
Example  2 . autoload parameter example

<?php
function __autoload($class)
{
    include($class . '.php');

    // Check to see if the include declared the class
    if (!class_exists($class, false)) {
        trigger_error("Unable to load class: $class", E_USER_WARNING);
    }
}

if (class_exists('MyClass')) {
    $myclass = new MyClass();
}

?>