Use $this->getDoctrine()->getManager() instead. Actually, it’s best not to make controllers aware of the persistence layer you’re using. That stuff should be moved to the Service Layer to abstract the way the data is persisted.
You can do $em->getRepository(Entity::class)->findBy(array(‘id’ => $idList));
This is a know issue where setFirstResult() and setMaxResults() need to be use with care if your query contains a fetch-joined collection. As stated about First and Max Result Items: If your query contains a fetch-joined collection specifying the result limit methods are not working as you would expect. Set Max Results restricts the number … Read more
Try passing the array itself to ->setParameter(…) instead of imploding it into a string.