title: Symfony2 - array to string conversion error
body: <p>I've read the other subjects but it doesn't solve my problem so:</p>
  
  <p>I've got this </p>
  
  <pre><code>-&gt;add('role', 'choice', array(
                  'label' =&gt; 'I am:',
                  'mapped' =&gt; true,
                  'expanded' =&gt; true,
                  'multiple' =&gt; false,
                  'choices' =&gt; array(
                      'ROLE_NORMAL' =&gt; 'Standard',
                      'ROLE_VIP' =&gt; 'VIP',
                  ) 
              ))
  </code></pre>
  
  <p>And whatever I do, I get this error:</p>
  
  <pre><code>Notice: Array to string conversion in C:\xampp\htdocs\xxx\vendor\symfony\symfony  \src\Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceList.php line 458 
  </code></pre>
  
  <p>In my form type the setRole method is not even called (when I rename it to some garbage the error still occurs). Why is this happening?</p>
  
  <p>// EDIT</p>
  
  <p>Full stack trace:</p>
  
  <pre><code>in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceList.php at line 458  -
  
       */
      protected function fixIndex($index)
      {
          if (is_bool($index) || (string) (int) $index === (string) $index) {
              return (int) $index;
          }
  
      at ErrorHandler -&gt;handle ('8', 'Array to string conversion', 'C:\xampp\htdocs     \xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceList.php', '458', array('index' =&gt; array()))
  in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceList.php at line 458  +
  at ChoiceList -&gt;fixIndex (array())
  in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceList.php at line 476  +
  at ChoiceList -&gt;fixIndices (array(array()))
  in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Extension\Core\ChoiceList\SimpleChoiceList.php at line 152  +
  at SimpleChoiceList -&gt;fixChoices (array(array()))
  in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceList.php at line 204  +
  at ChoiceList -&gt;getIndicesForChoices (array(array()))
  in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Extension\Core\DataTransformer\ChoiceToBooleanArrayTransformer.php at line 63  +
  at ChoiceToBooleanArrayTransformer -&gt;transform (array())
  in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Form.php at line 1019  +
  at Form -&gt;normToView (array())
  in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Form.php at line 332  +
  at Form -&gt;setData (array())
  in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Extension\Core\DataMapper\PropertyPathMapper.php at line 59  +
  at PropertyPathMapper -&gt;mapDataToForms (object(User), object(RecursiveIteratorIterator))
  in C:\xampp\htdocs\xxx\vendor\symfony\symfony\src\Symfony\Component\Form\Form.php at line 375  +
  at Form -&gt;setData (object(User))
  in C:\xampp\htdocs\xxx\vendor\friendsofsymfony\user-bundle\FOS\UserBundle\Controller\RegistrationController.php at line 49  +
  at RegistrationController -&gt;registerAction (object(Request))
  at call_user_func_array (array(object(RegistrationController), 'registerAction'), array(object(Request)))
  in C:\xampp\htdocs\xxx\app\bootstrap.php.cache at line 2770  +
  at HttpKernel -&gt;handleRaw (object(Request), '1')
  in C:\xampp\htdocs\xxx\app\bootstrap.php.cache at line 2744  +
  at HttpKernel -&gt;handle (object(Request), '1', true)
  in C:\xampp\htdocs\xxx\app\bootstrap.php.cache at line 2874  +
  at ContainerAwareHttpKernel -&gt;handle (object(Request), '1', true)
  in C:\xampp\htdocs\xxx\app\bootstrap.php.cache at line 2175  +
  at Kernel -&gt;handle (object(Request))
  in C:\xampp\htdocs\xxx\web\app_dev.php at line 29  +
  </code></pre>