public static function getSessionToken()
    {
        $token = null;

        if (isset($_SESSION[__SYM_COOKIE_PREFIX__]['xsrf-token'])) {
            $token = $_SESSION[__SYM_COOKIE_PREFIX__]['xsrf-token'];
        }

        if (is_array($token)) {
            $token = key($token);
        }

        return is_null($token) ? null : $token;
    }