title: symfony 2 choice ajax validation fix
body: <p>I try something like that - <a href="https://stackoverflow.com/questions/12946461/validating-dynamically-loaded-choices-in-symfony-2">Validating dynamically loaded choices in Symfony 2</a> </p>
  
  <p>but this when we get submited form check possible values - in my sitation any is correct. </p>
  
  <p>i add modification to allow any value - like here </p>
  
  <pre><code>$builder-&gt;addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event) {
          $data = $event-&gt;getData();
          $event-&gt;getForm()-&gt;add('tags', 'tag', [
              'label'   =&gt; 'Sub Choice',
              'choices' =&gt; $data['tags'],
              'mapped'=&gt;false,
              'required'=&gt;false,
              'multiple'=&gt;true,
          ]);
      });
  </code></pre>
  
  <p>but it not work - how to make it usable ?</p>
  
  <p>tag is my input extens of choice (for js ajax chosen) </p>