Persistencia de Entidades vinculadas

Crear un registro de entidad asociada:

addComment($myFirstComment);

$em->persist($user);
$em->persist($myFirstComment);
$em->flush();

Eliminar en cascada:

$user = $em->find('User', $deleteUserId);

foreach ($user->getAuthoredComments() AS $comment) {
    $em->remove($comment);
}
$em->remove($user);
$em->flush();