``` // 添加 $activity = new ModelActivity; $activity->startTrans(); try { $activity->save([ 'type' => $type]); $activity->commit(); } catch (\Exception $e) { $activity->rollback(); } // 修改 $activity = ModelActivity::findOrEmpty($id); $activity->startTrans(); try { $activity->save([ 'type' => $type]); $activity->commit(); } catch (\Exception $e) { $activity->rollback(); } ```