title: Make a Successive form
body: <p>I want to make successive form with Symfony 2.7 (2 forms) but I can not. The second form uses data from the first.</p>
  
  <p>I tried this :</p>
  
  <pre><code>   if($request-&gt;getMethod() === 'POST') {
          $lot = new Lot();
          if($request-&gt;request-&gt;has('logiciel_version_debut_form')) {
              /*
                  SEND FIRST VALUE FORM
              */
              $lot-&gt;setDateDebut(new \DateTime($request-&gt;get('logiciel_version_debut_form')['date_debut']['year'] . '-' . $request-&gt;get('logiciel_version_debut_form')['date_debut']['month'] . '-' . $request-&gt;get('logiciel_version_debut_form')['date_debut']['day']));
          }
          /*
              SECOND FORM FORM
          */
          $form = $this-&gt;createForm('logiciel_lot_form', $lot);
          $this-&gt;submit($form);
          if ($form-&gt;handleRequest($request)-&gt;isValid()) {
              /*
                  OK GOOD :-)
              */
          }
      } else {
          /*
              FIRST FORM
          */
          $form = $this-&gt;createForm('logiciel_version_debut_form');
          $this-&gt;submit($form);
      }
      return array(
          'form' =&gt; $form-&gt;createView(),
          'title' =&gt; 'Ajouter un nouveau lot'
      );
  </code></pre>
  
  <p>But it does not test if the first is valid. Can you help me ?</p>