public function getAccessToken($oauth_token)
    {
        $accessToken = $this->em->getRepository('OAuth2ServerBundle:AccessToken')->find($oauth_token);

        if (!$accessToken) {
            return null;
        }

        // Get Client
        $client = $accessToken->getClient();

        return array(
            'client_id' => $client->getClientId(),
            'user_id' => $accessToken->getUserId(),
            'expires' => $accessToken->getExpires()->getTimestamp(),
            'scope' => $accessToken->getScope()
        );
    }