title: Selecting multiple items by default in sfWidgetFormDoctrineChoice (symfony)
body: <p>Using Symfony and Doctrine, I have a multi-select list box.  The multiple default values need to be generated based on a Doctrine query.</p>
  
  <pre><code>$this-&gt;setWidgets(array(
    'folders' =&gt; new sfWidgetFormDoctrineChoice(array(
      'model' =&gt; 'FolderItem',
      'order_by' =&gt; array('name', 'asc'),
      'multiple' =&gt; true,
      'query' =&gt; FolderItemTable::getUserInstance($user),
    ))
  ));
  </code></pre>
  
  <p>This gets me a list of all my folder items; however, I want them pre-selected by a list of Folders.  For example, if I have <code>Folder 1</code> containing <code>item a</code> <code>item b</code> and <code>item c</code>  and <code>Folder 2</code> containing <code>item d</code> and <code>item e</code>; if <code>Folder 1</code> is passed in I want <code>item a</code> <code>item b</code> and <code>item c</code> to be selected, but I want <code>item d</code> and <code>item e</code> in the list but not selected (but selectable)</p>