autoload does not work

#!/opt/local/bin/php
<?php
namespace VhostsManager;

/**
 * autoload needed classes
 */
function __autoload( $class ){
    require_once 'classes/' . $class . '.php';
}

$operation = $argv[1];
$localdomain = $argv[2];
$directory = $argv[3];

/**
 * Check for used operation and run appropriate functions.
 */

switch($operation) {
	case 'create':
		$virtualhost = new VhostDebug($localdomain, $directory);
		$virtualhost->createVhost();
		break;

	case 'delete':
		echo 'Deleting a Vhost is not supported right now.';
		break;
	case 'edit':
		echo 'Editing a Vhost is not supported right now.';
		break;
	default:
		echo 'You entered a wrong command. [create|delete|edit]';
}
?>