LeadMatchingOfficeViewingsType.php

class LeadMatchingOfficeViewingsType extends AbstractType
{
    public function buildForm(FormBuilder $builder, array $options)
    {
        $builder
			->add('viewings', 'collection', array(
				'type' => new ViewingsListType()
			))
		;
	}

    public function getName()
    {
        return 'phoenix_crmbundle_leadmatchingofficeviewingstype';
    }
}

LeadViewingsType.php

class LeadViewingsType extends AbstractType
{
    public function buildForm(FormBuilder $builder, array $options)
    {
        $builder
			->add('lead_matching_offices', 'collection', array(
				'type' => new LeadMatchingOfficeViewingsType()
			))
		;
	}

	public function getName()
	{
		return 'phoenix_crmbundle_leadviewings';
	}
}

Output

var_dump([errors])
-------------------
array (size=2)
  0 => string 'This form should not contain extra fields' (length=41)
  'phoenix_crmbundle_leadviewings' => 
    array (size=1)
      0 => string 'This form should not contain extra fields' (length=41)

var_dump($request->request->all())
----------------------------------
array (size=1)
  'phoenix_crmbundle_leadviewings' => 
    array (size=2)
      '_token' => string '520f9d6316f43313bdb1ae6eee250ee4925c5593' (length=40)
      'lead_matching_offices' => 
        array (size=1)
          0 => 
            array (size=1)
              'viewings' => 
                array (size=1)
                  0 => 
                    array (size=1)
                      'cancel' => string '1' (length=1)

ViewingsListType.php

class ViewingsListType extends AbstractType
{
    public function buildForm(FormBuilder $builder, array $options)
    {
        $builder
			->add('cancel', 'checkbox', array(
				'property_path' => false	
			))
		;
	}

    public function getName()
    {
        return 'phoenix_crmbundle_viewingslisttype';
    }
}