/**
  * This method return a singleton instance of __ExceptionFactory
  *
  * @return __ExceptionFactory A singleton reference to the __ExceptionFactory
  */
 public static function &getInstance()
 {
     if (self::$_instance == null) {
         // Use "Lazy initialization"
         self::$_instance = new __ExceptionFactory();
     }
     return self::$_instance;
 }