title: Doctrine, escape variable field name in DQL
body: <p>I have a DQL query like:</p>
  
  <pre><code>$em-&gt;createQuery("
      SELECT r
      FROM WeAdminBundle:FamilyRelation r
      WHERE r.col like :query
  ")
  </code></pre>
  
  <p>Now I want to change "col" depending on various parameters. How can i achieve this with DQL since the normal setParameter doesn't work here.</p>