title: Laravel orderBy on a relationship
body: <p>I am looping over all comments posted by the Author of a particular post.</p>
  <pre><code>foreach($post-&gt;user-&gt;comments as $comment)
  {
      echo &quot;&lt;li&gt;&quot; . $comment-&gt;title . &quot; (&quot; . $comment-&gt;post-&gt;id . &quot;)&lt;/li&gt;&quot;;
  }
  </code></pre>
  <p>This gives me</p>
  <pre><code>I love this post (3)
  This is a comment (5)
  This is the second Comment (3)
  </code></pre>
  <p>How would I order by the post_id so that the above list is ordered as 3,3,5</p>