title: infinite loop in a WebHook
body: <p>I'm doing a facebook messenger bot. After you start it, it makes a call to WebHook. 
  Unfortunately after the first start will not stop throwing the same call with the same parameters.
  The settings are:</p>
  
  <ul>
  <li>message_deliveries;</li>
  <li>message_reads;</li>
  <li>messages;</li>
  <li>messaging_optins;</li>
  <li>messaging_postbacks.</li>
  </ul>
  
  <p>The source code is this: <a href="https://github.com/Ellusu/nuraghebot-facebookmessenger/blob/master/index.php">https://github.com/Ellusu/nuraghebot-facebookmessenger/blob/master/index.php</a></p>
  
  <p>Where am I wrong?
  Why does only one call?</p>