ModelListExtension.php

<?php
// florin 3/25/14 2:16 PM
namespace Wyzbiz\Bundle\MainBundle\Form\Extension;

use Symfony\Component\Form\AbstractTypeExtension;
use Symfony\Component\Form\FormView;
use Symfony\Component\Form\FormInterface;
use Symfony\Component\PropertyAccess\PropertyAccess;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

class ModelListExtension extends AbstractTypeExtension
{
    public function getExtendedType()
    {
        return 'sonata_type_model_list';
    }

    /**
     * Add the multiple option
     *
     * @param OptionsResolverInterface $resolver
     */
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setOptional(array('multiple'));
    }
}