private function parseTokenString($response)
    {
        $parts = explode('&', $response);
        $token = new \stdClass();
        foreach ($parts as $part) {
            list($k, $v) = explode('=', $part, 2);
            $k = strtolower($k);
            $token->$k = $v;
        }
        return $token;
    }