yii2开启事务

 public function actionAdd()
    {
        $model = new Goods();
        $model->setScenario('insert');

        if ($model->load(Yii::$app->request->post())) {

            $model->image = UploadedFile::getInstance($model, 'image');

            if ($model->validate()) {

                $model->cover = Yii::$app->security->generateRandomString() . '.' . $model->image->extension;
                if (floatval($model->price_original) < 0.01) {
                    $model->price_original = null;
                }

                $transaction = Yii::$app->db->beginTransaction();
                try {
                    if (!$model->save(false)) {
                        throw new \Exception('商品添加失败！');
                    }

                    $filename = Yii::getAlias(Yii::$app->params['goods.coverPath']) . DIRECTORY_SEPARATOR . $model->cover;
                    if (!$model->image->saveAs($filename)) {
                        throw new \Exception('封面图片添加失败！');
                    }

                    // 记录商品库存
                    $goodsSurplus = new GoodsSurplus();
                    $goodsSurplus->goods_id = $model->id;
                    $goodsSurplus->surplus_before = ;
                    $goodsSurplus->amount = $model->surplus;
                    $goodsSurplus->surplus_after = $model->surplus;
                    $goodsSurplus->remark = '初始化库存。';

                    if (!$goodsSurplus->save(false)) {
                        throw new \Exception('商品库存记录失败！');
                    }

                    $transaction->commit();
                    Yii::$app->session->setFlash('success', '成功添加商品“'.$model->name.'”。');
                    return $this->refresh();
                } catch (\Exception $e) {
                    $transaction->rollBack();
                    Yii::$app->session->setFlash('danger', $e->getMessage());
                }
            }
        }

        return $this->render('form', [
            'model' => $model
        ]);
    }