title: How to pre-select a form radio item with Symfony 2?
body: <p>I'm working on a language choice form:</p>
  
  <pre><code>    $currentLocale = "en_US"; // This is indeed sent to the formType
  
      $langs = array(
          'fr_FR' =&gt; 'fr',
          'en_US' =&gt; 'en'
          );
  
      $builder-&gt;add('language', 'language', array(
          'choices' =&gt; $langs,
          'expanded' =&gt; true,
          'multiple' =&gt; false,
          'required' =&gt; false,
          'label' =&gt; false,
      ));
  </code></pre>
  
  <p>The HTML code looks like this (simplified):</p>
  
  <pre><code>&lt;div id="languageForm_language"&gt;
      &lt;input type="radio" value="fr_FR"&gt;
      &lt;input type="radio" value="en_US"&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>How could I get the second item pre-selected, according to the <code>$currentLocale</code> value ?</p>