pay_center_server/app/Models/OrderModel.php

<?php

namespace App\Models;

class OrderModel extends BaseModel
{
    protected $table = 'order';

    public function merchant()
    {
        return $this->hasOne(MerchantModel::class, 'uid', 'merchant_uid');
    }

    public function payment()
    {
        return $this->hasOne(PaymentModel::class, 'uid', 'payment_uid');
    }

    public function paymentAttr()
    {
        return $this->hasOne(PaymentAttrModel::class, 'uid', 'payment_attr_uid');
    }
}