title: How to pass twig parameters through FormBuilder's fields
body: <p>I've implemented the help messages in forms as in the <a href="http://symfony.com/doc/current/cookbook/form/form_customization.html#adding-help-messages" rel="nofollow">documentation</a></p>
  
  <pre><code>{% extends 'form_div_layout.html.twig' %}
  
  {% block field_widget %}
      {{ parent() }}
      {% if help is defined %}
          &lt;span class="help"&gt;{{ help }}&lt;/span&gt;
      {% endif %}
  {% endblock %}
  </code></pre>
  
  <p>To render the help section, the example says that 'help' should be defined in the twig file as in:</p>
  
  <pre><code>{{ form_widget(form.title, {'help': 'foobar'}) }}
  </code></pre>
  
  <p>However, I'd like to define 'help' as an option for the fields in the form builder, like this:</p>
  
  <pre><code>class myClassType extends AbstractType
  {
      public function buildForm(FormBuilder $builder, array $options)
      {
          $builder
              -&gt;add('title',null,array('help'=&gt;'foobar'));
      }
  }
  </code></pre>
  
  <p>This has yield no results ("The option "help" does not exist "). I've also tried</p>
  
  <pre><code>$builder
     -&gt;add('title',null,array('attr'=&gt;array(help'=&gt;'foobar')));
  </code></pre>
  
  <p>and it doesn't work either.</p>
  
  <p>Any ideas to get something like this working?</p>