title: Facebook PHP API issues with subscription
body: <p>I'm trying to use Facebook's realtime updates as described <a href="https://developers.facebook.com/docs/reference/api/realtime/" rel="nofollow">here</a>. I'm using the PHP SDK. I already have an access token that works for other functions with these permissions: usser_checkins,publish_stream,offline_access.</p>
  
  <p>When trying to add the subscription I receive the following error from the Facebook SDK.</p>
  
  <blockquote>
    <p>Fatal error: Uncaught OAuthException: (#15) This method must be called with an app access_token</p>
  </blockquote>
  
  <p>The code I am using is below. All the variables are set correctly. Any ideas?</p>
  
  <pre><code>    $callback_url = plugins_url('fb_callback.php',__FILE__);
      $config = array('appId' =&gt; $app_id,
                      'secret' =&gt; $app_secret,
                       );
      $facebook = new Facebook($config);
      $token = fb_get_access_token();
      $facebook-&gt;setAccessToken($token);
      $ret_obj = $facebook-&gt;api($app_id . '/subscriptions', 'POST',
                  array('callback_url' =&gt; $callback_url,
                        'object' =&gt; 'checkin',
                        'verify_token' =&gt; 'a390jkl091091j908j',
                        'fields' =&gt; 'id'
                        ));
  </code></pre>