title: Add form fields to symfony collection type
body: <p>Hello I have been struggling with a problem for some days now.</p>
  
  <p>I have a form type which has a collection type field. I want to add elements to the collection field in the buildform method of my form type.</p>
  
  <p>Here is my code :</p>
  
  <pre><code>    $builder  
          -&gt;add('cIName', 'text')
          -&gt;add('cIAttributes', 'collection', array(
              'label' =&gt;false
          ))
      ;
  
      $builder-&gt;get('cIAttributes')-&gt;add('cIDescription', 'textarea');
  </code></pre>
  
  <p>Unfortunately it doesn't work. Can anyone tell me what I'm doing wrong or what I need to do ?</p>