title: Customizing twig form template for inputs inside containers in symfony2
body: <p>I have a FormType that have this datetime input:</p>
  
  <pre><code>    $builder-&gt;add('data_inicio', 'datetime', array(
          'input' =&gt; 'datetime',
          'date_widget' =&gt; 'single_text',
          'time_widget' =&gt; 'choice',
          'attr' =&gt; array(
              'class' =&gt; 'datetime rangeDataInicio',
              'maxlength' =&gt; '10',
              'placeholder' =&gt; 'dd/mm/aaaa',
          ),
          'date_format' =&gt; 'dd/MM/yyyy',
          'required' =&gt; true,
          'disabled' =&gt; $isDisabled,
      ));
  </code></pre>
  
  <p>Form some reasons, I have to insert the placeholder and the class direct at the single_text date input, but both of them stays at the container and don't go to the input.</p>
  
  <p>I tried a several ways to do this and all of them failed and searched the web for a couple of weeks and found nothing that could sove my problem. How can I put these two attrs at the input?</p>