protected static function _cleanPrevious()
		{
			if(self::$_cleanedPrev) return true;
			self::$_cleanedPrev = 1;

			if(isset($_SESSION) && is_array($_SESSION)) {
                foreach ($_SESSION as $key => $value) {
                    if (strpos($key, self::$_sessionKey) === 0) {
                        if ($_SESSION[$key][0] < 1) {
                            unset($_SESSION[$key]);
                        } else {
                            $_SESSION[$key][0] = 0;
                        }
                    }
                }
            }
		}