public function isUnlockedDrop($dropzoneId, $userId)
    {
        $qb = $this->createQueryBuilder('drop')
            ->select('drop.unlockedUser')
            ->andWhere('drop.dropzone = :dropzone')
            ->andWhere('drop.user = :user')
            ->setParameter('dropzone', $dropzoneId)
            ->setParameter('user', $userId);
        $isUnlockedDrop = $qb->getQuery()->getOneOrNullResult();

        return $isUnlockedDrop;
    }