title: How to reply private message with facebook api
body: <p>I've managed to do a reading of the data on the facebook page private message me. Then I want to reply to the sender but failed. </p>
  
  <p>My app permission : <code>manage_pages, read_page_mailboxes</code></p>
  
  <p>My code :</p>
  
  <pre><code>require '../src/facebook.php';
  $facebook = new Facebook(array(
    'appId'  =&gt; '339554932xxxxxx',
    'secret' =&gt; 'zzz334534123xx',
  ));
  
  $pages = $facebook-&gt;api('/me/accounts');
  
  foreach ($pages['data'] as $page) {
          $page_access_token = $page['access_token'];
  }
  
  $MsgRep = "This is a reply message...";
  $MID    = "m_mid.1393481292907:f67352f5dfd39b5e42";
  $facebook-&gt;api('/'.$MID.'/messages', 'POST', array('message' =&gt;$MsgRep, 'access_token' =&gt; $page_access_token));
  echo "Message Sent";
  </code></pre>
  
  <p>The result: But I just get a blank screen. without <code>echo "Message Sent"</code></p>
  
  <p>Is there something wrong with my code?</p>
  
  <p>Thanks</p>