if (!$users = $DB->get_records_sql("SELECT $userfields

                                                  FROM {course_modules} cm

                                                  JOIN {chat} ch        ON ch.id = cm.instance

                                                  JOIN {chat_users} chu ON chu.chatid = ch.id

                                                  JOIN {user} u         ON u.id = chu.userid

                                                 WHERE cm.id = :cmid $timeout $groupselect

                                              GROUP BY $userfields", $params)) {

            }