title: Symfony 2 Form collection field with type file
body: <p>I want to upload multiple files with POST request (without Ajax). Can I use Symfony 2's form collection field with type file like this:  </p>
  
  <p>Code in Entity:</p>
  
  <pre class="lang-php prettyprint-override"><code>public $pictures;
  
  public function __construct()
  {
      $this-&gt;pictures = new \Doctrine\Common\Collections\ArrayCollection();
  }
  </code></pre>
  
  <p>Code in Form Class:</p>
  
  <pre class="lang-php prettyprint-override"><code>$builder-&gt;add('pictures', 'collection', array(
          'type' =&gt; 'file',
          'required' =&gt; false,
          'attr' =&gt; array(
              'multiple' =&gt; 'multiple'
          )
  ));
  </code></pre>
  
  <p>Code in Twig:</p>
  
  <pre class="lang-html prettyprint-override"><code>{% for picture in form.pictures %}
      &lt;td&gt;
          {{ form_widget(picture) }}
      &lt;/td&gt;
  {% endfor %}
  </code></pre>
  
  <p>I tried, but it doesn't seem to work. It is not showing any errors, but it is not showing the input file either. Any ideas?</p>