I would like to use some MySQL functions such as DATE_FORMAT in my QueryBuilder.

I saw this post did not understand totally how I should achieve it: SELECT DISTINCT YEAR Doctrine

class SubmissionManuscriptRepository extends EntityRepository
{
    public function findLayoutDoneSubmissions( $fromDate, $endDate, $journals )
    {
        if( true === is_null($fromDate) )
            return null;

        $commQB = $this->createQueryBuilder( 'c' )
                    ->join('c.submission_logs', 'k')
                    ->select("DATE_FORMAT(k.log_date,'%Y-%m-%d')")
                    ->addSelect('c.journal_id')
                    ->addSelect('COUNT(c.journal_id) AS numArticles');

        $commQB->where("k.hash_key = c.hash_key");
        $commQB->andWhere("k.log_date >= '$fromDate'");
        $commQB->andWhere("k.log_date <= '$endDate'");
        if( $journals != null && is_array($journals) && count($journals)>0 )
        $commQB->andWhere("c.journal_id in (" . implode(",", $journals) . ")");
        $commQB->andWhere("k.new_status = '20'");
        $commQB->orderBy("k.log_date", "ASC");
        $commQB->groupBy("c.hash_key");
        $commQB->addGroupBy("c.journal_id");
        $commQB->addGroupBy("DATE_FORMAT(k.log_date,'%Y-%m-%d')");

        return $commQB->getQuery()->getResult();
    }
}

Entity SubmissionManuscript

/**
 * MDPI\SusyBundle\Entity\SubmissionManuscript
 *
 * @ORM\Entity(repositoryClass="MDPI\SusyBundle\Repository\SubmissionManuscriptRepository")
 * @ORM\Table(name="submission_manuscript")
 * @ORM\HasLifecycleCallbacks()
 */
class SubmissionManuscript
{
    ...

    /**
         *   @ORM\OneToMany(targetEntity="SubmissionManuscriptLog", mappedBy="submission_manuscript")
         */
     protected $submission_logs;

        ...
}

Entity SubmissionManuscriptLog

/**
 * MDPI\SusyBundle\Entity\SubmissionManuscriptLog
 *
 * @ORM\Entity(repositoryClass="MDPI\SusyBundle\Repository\SubmissionManuscriptLogRepository")
 * @ORM\Table(name="submission_manuscript_log")
 * @ORM\HasLifecycleCallbacks()
 */
class SubmissionManuscriptLog
{
    ...

    /**
     * @ORM\ManyToOne(targetEntity="SubmissionManuscript", inversedBy="submission_logs")
     * @ORM\JoinColumn(name="hash_key", referencedColumnName="hash_key")
     */
    protected $submission_manuscript;

    ...
}

any help I would appreciate a lot.

EDIT 1

I have now successfully be able to add the Custom Function DATE_FORMAT. But now if I try with my Group By I get the following Error:

[Semantical Error] line 0, col 614 near '(k.logdate,'%Y-%m-%d')': Error: Cannot group by undefined identification variable.

Anyone knows about this?