public function register()
    {
        if (PHP_VERSION_ID >= 50400) {
            session_set_save_handler($this, true);
        } else {
            session_set_save_handler(
                array($this, 'open'),
                array($this, 'close'),
                array($this, 'read'),
                array($this, 'write'),
                array($this, 'destroy'),
                array($this, 'gc')
            );
        }
    }