$create = [
            'title' => $data['title'],
            'describes' => $data['introduce'],
            'promotions_detail' => json_encode([
                'type' => $data['discount_type'],
                'point' => $data['discount']
            ]),
            'time_limit' => $data['deadline'],
            'extend' => json_encode($data),
            'status' => 1
        ];
        $res = Coupon::create($create);

通过这样写入数据库会报错，请问什么原因，php7.2的版本