Sulu\Bundle\MediaBundle\Entity\CollectionRepository::findCollectionTypeById PHP Method

    public function findCollectionTypeById($id)
    {
        $queryBuilder = $this->createQueryBuilder('collection')->select('collectionType.key')->leftJoin('collection.type', 'collectionType')->where('collection.id = :id')->setParameter('id', $id);
        return $queryBuilder->getQuery()->getSingleScalarResult();
    }