private function cleanMessages($document_id)
{
if ($clients = TlonUserDocument::getByDocumentID($document_id)) {
$oldest_client = 0;
foreach ($clients as $client) {
if ($client['last_updated'] < $oldest_client || $oldest_client == 0) {
$oldest_client = $client['last_updated'];
}
}
if ($oldest_client != 0) {
TlonMessage::deleteByArrivalTimeBefore($oldest_client);
}
}
}
