title: How to to return most recent data using group by and order by
body: <p>I have seen many posts but nothing is wokring. It seems group by always group the oldest one. I want to group the result and pick the most recent one. 
  Here is my query </p>
  
  <pre><code>Message::whereIn('conversation_id',$msgs)
               -&gt;orderBy('created_at', 'desc') 
               -&gt;groupBy('conversation_id')
               -&gt;with(array('last_sender'=&gt;function($query){
                      $query-&gt;select('id','userName','profilePic', 'firstName','lastName');
                }))
              -&gt;get();
  </code></pre>