Simple doctrine find last modified thing

findLastModifiedThing.php

<?php

/**
 * @return null|\DateTime
 */
public function findLastModifiedThing()
{
    $query = $this->createQueryBuilder('t')
        ->select('t.updated_at')
        ->orderBy('t.updated_at', 'desc')
        ->setMaxResults(1);

    $result = $query->getQuery()->getOneOrNullResult();

    return null == $result ? null : $result['updated_at'];
}