title: Doctrine, remove collection?
body: <p>I need to remove a collection with Doctrine with Symfony2.</p>
  
  <p>So, i retrieve all objects like that :</p>
  
  <pre><code>$comments = $em-&gt;getRepository('ProjectApplicationBundle:Comment')-&gt;findBy(array('user_id' =&gt; $user_id));
  </code></pre>
  
  <p>So, with this, i can retrieve a lots of comments.</p>
  
  <p>How can i remove these comments ? A simple <code>$em-&gt;remove($comments)</code> don't work.</p>
  
  <p>A need to loop comments and remove each element ? It is better to write the query directly ?
  Any better ways ? Thanks</p>