Symfony2: Inserting a collection of files

Question

While trying to insert a collection of entities which have a file field, i couldn't figure out if there's is a better way to create the UploadedFile Object being cast by the Document::document annotation. Here's my code, any help on improving it is very appreciated :)

public function createAction(Request $request) {
    $em = $this->getDoctrine()->getManager();

    $user = $this->get('security.context')->getToken()->getUser();
    $entity = new Paper();
    $form = $this->createCreateForm($entity);
    $form->handleRequest($request);

    if ($form->isValid()) {

        $entity->setAuthor($user);
        $em->persist($entity);

        // chotest foreach in the universe
        if (isset($_FILES) && array_key_exists('arkad1a_cfpbundle_paper', $_FILES)) {
            foreach ($_FILES['arkad1a_cfpbundle_paper']['name']['documents'] as $k => $v) {
                $document = new UploadedFile(
                    $_FILES['arkad1a_cfpbundle_paper']['tmp_name']['documents'][$k]['document'],
                    $_FILES['arkad1a_cfpbundle_paper']['name']['documents'][$k]['document'],
                    $_FILES['arkad1a_cfpbundle_paper']['type']['documents'][$k]['document'],
                    $_FILES['arkad1a_cfpbundle_paper']['size']['documents'][$k]['document'],
                    $_FILES['arkad1a_cfpbundle_paper']['error']['documents'][$k]['document'],
                    false
                );

                $Document = new \Arkad1a\CFPBundle\Entity\Document();
                $Document->setAuthor($user)
                        ->setDocument($document)
                        ->setPaper($entity)
                        ->upload();
                $em->persist($Document);
            }
        }

        $em->flush();

        return $this->redirect($this->generateUrl('paper_show', array('id' => $entity->getId())));
    } else {
        die('invalid');
    }

    return array(
        'entity' => $entity,
        'form' => $form->createView(),
    );
}