$form = $this->createFormBuilder();
$registration = $this->get('form.factory')->createNamedBuilder('registration');
$questionary = $this->get('form.factory')->createNamedBuilder('questionary');

$registration
  ->add('name', 'text')
  ->add('city', 'text')
  ;

$questionary
  ->add('question_1', 'text')
  ->add('question_2', 'choice', array(
    'choices' => array('female', 'male')
  ))
  ;

$form->add($registration);
$form->add($questionary);
?>

{{ form_row(form.registration) }}
{{ form_row(form.questionary) }}

<?
$data = $form->getData();
$registration = $data['registration'];
$questionary = $data['questionary'];