php – Symfony表单Select2允许用户输入新值

->add('province','entity',array(
                'class' => 'PNCGeneralBundleEntityState','property' => 'name','empty_value'=>'-- Select Province --','label' => ucfirst('State / Province / Region'),'required'  => false,'attr' => array('class' => 'form-control'),'label_attr' => array('class' => 'control-label'),'mapped' => false,))

枝条

$('#user_profile_type_province').select2({
    tags: "true",});

调节器

if ($request->getMethod() == 'POST') {
 $UserProfileForm->handleRequest($request);
 $province = $UserProfileForm["province"]->getData();
 $tag = $em->getRepository('PNCGeneralBundle:State')->findOneByName($province);
 if(!$tag){
   $newState = new State();
   $newState->setName($province);
   $newState->setCountry($UserProfileForm["country"]->getData());
   $em->persist($newState);
   $em->flush();
   }
}

但是当我在省select2中输入新内容时,我的省值为null.