public function findByTag($tag)
    {
        return $this->createQueryBuilder('p')
            ->join('p.tags', 't')
            ->where('p.active = true')
            ->andWhere('t.name = :name')
            ->setParameter('name', $tag)
            ->orderBy('p.datePublished', 'DESC')
            ->getQuery()
            ->getResult();
    }