UserEmail.php

    public function isEmailUnique($email_address)
    {
        $qb = $this->createQueryBuilder('e')
            ->select('COUNT(e.id)')
            ->where('e.email_address = :email')
            ->setParameter('email', $email_address);

        $result = $qb->getQuery()->getSingleScalarResult();

        if ($result > 0)
            return false;
        return true;
    }