title: Where Method not working in Doctrine Query Builder?
body: <p>I have the ff basic query. The query works fine without WHERE method being called. </p>
  
  <pre><code>$qb-&gt;select(array('m', 'c'))
             -&gt;from('models\Book', 'm')
             -&gt;leftJoin('m.Chapters', 'c')
             -&gt;where('m.Slug=?', $slug)
             -&gt;orderBy('c.CreateDate', 'DESC');
  </code></pre>
  
  <p>But after I call it with WHERE method in Doctrine. The ff. "hard to understand error" appear:</p>
  
  <pre><code>Uncaught exception 'Doctrine\ORM\Query\QueryException' with message 'Invalid parameter format, ? given, but :&lt;name&gt; or ?&lt;num&gt; expected.' 
  </code></pre>
  
  <p>What could be the solution for this problem?</p>