PHP Singleton class, simple usage

PHP Singleton

<?php

class MyClass 
{
    private static $instance = null;
    private function __construct() { }
    public static function getInstance()
    {
       if(self::$instance == null)
       {   
          $c = __CLASS__;
          self::$instance = new $c;
       }
       return self::$instance;
    }
}

?>