1.为什么要有状态机？状态机又是什么？
有些订单的状态，任务的状态过于复杂，状态机是为了方便我们管理整个任务，订单的状态，防止错误的状态切换。毕竟现在都是团队合作。有一个模型来管理，也好规范其它程序员代码质量。

2.订单状态机

namespace app\api\service;

class OrderService
{
    //订单状态可以考虑成int 类型，mysql检索速度快
    public static $STATUS_NEW = 'new';   //新订单
    public static $STATUS_PAYED = 'payed'; //已支付
    public static $STATUS_DELIVERY = 'delivery'; //已发货
    public static $STATUS_RECEIVED = 'received'; //收货
    public static $STATUS_COMPLETE = 'complete';  //已完成

    private static $ALLOW_CHANGE_STATUS = [
        'new' => ['payed'],
        'payed' => ['delivery'],
        'received' => ['received'],
        'delivery' => ['complete'],
    ];

    /**
     * 状态切换
     * @param $status
     * @param $data
     * @throws \Exception
     */
    public function changeStu($status, $data)
    {
        //check order status
        $order=Order::find($data['orderNo']);
        if(!in_array($status,self::$ALLOW_CHANGE_STATUS[$order['status']])){
            throw new \Exception(' order status error');
        }
        
        
    }

    /**
     *  订单管理
     * @param $status
     * @param $data
     * @return bool|void
     */
    public function dispatch($status, $data)
    {
        $result = false;
        switch ($status) {
            case self::$STATUS_NEW:
                $result = self::createNew($data);
                break;
            case self::$STATUS_PAYED:
                $result = self::payed($data);
                break;
            case self::$STATUS_DELIVERY:
                $result = self::delivery($data);
                break;
            case self::$STATUS_RECEIVED:
                $result = self::received($data);
                break;
            case self::$STATUS_COMPLETE:
                $result = self::complete($data);
                break;
            default:
                $result = false;
        }
        return $result;
    }


    //各自功能实现
    private static function createNew($data)
    {
        //create new order
    }

    private static function payed($data)
    {
        //make the order payed
    }

    private static function delivery($data)
    {
        //make the order delivery
    }

    private static function received($data)
    {
        //make the order reveived
    }

    private static function complete($data)
    {
        //make the order complete
    }


}