支付宝的demo：https://docs.open.alipay.com/270/106291/
一般是在notify_url 异步通知 里写业务代码。return_url只做付款成功后展示页。

要点

notify_url 要能直接访问到，不能有登录密码之类
写完后发现成功返回return_url，却进入不了notify_url的post，原来是外部无法访问，果断禁用登录访问

public $enableCsrfValidation = false;  //关闭csrf验证，允许表单多次提交
public $layout=false;  //禁用框架，包括不登录无法访问功能

controller

    public function actionServermoney1()
    {
        $thirdid = Yii::$app->user->identity->thirdid;
            $money = 0.01;
            $randstr = RechargeController::getrandstr();
            $out_trade_no = 'servermoney' . $randstr . '-' . time();

            $models = new IbdThirdServicemoney();
            $models->money = $money*100;
            $models->time = time();
            $models->thirdid = $thirdid;
            $models->status = 0;
            $models->tradeno = $out_trade_no;
            $models->save();
            //构造参数
            $payRequestBuilder = new  \AlipayTradePagePayContentBuilder();

            $payRequestBuilder->setSubject('开通服务费');
            $payRequestBuilder->setTotalAmount($money);

            $payRequestBuilder->setOutTradeNo($out_trade_no);
            $config=Yii::$app->params['config2'];
            $aop = new \AlipayTradeService($config);
            /**
             * pagePay 电脑网站支付请求
             * @param $builder 业务参数，使用buildmodel中的对象生成。
             * @param $return_url 同步跳转地址，公网可以访问
             * @param $notify_url 异步通知地址，公网可以访问
             * @return $response 支付宝返回的信息
             */
            $response = $aop->pagePay($payRequestBuilder, $config['return_url'], $config['notify_url']);
            $json["status"] = 1;
            $json["data"] = $response;
            var_dump($response);
            die;
    }

params

'config2'=>[
        'app_id' => "支付宝app_id",
        'merchant_private_key' => "key1",
        'notify_url' => "网站地址/third/notice/alinotify",
        'return_url' => "网站地址/third/recharge/alireturn",
        'charset' => "UTF-8",
        'sign_type'=>"RSA2",
        'gatewayUrl' => "https://openapi.alipay.com/gateway.do",
        'alipay_public_key' => "key2",
    ],

NoticeController

<?php
namespace third\controllers;


use common\models\GIm;
use Yii;
use \yii\filters\AccessControl;
use \yii\web\Controller;

require_once dirname(dirname(__DIR__)) . '/vendor/alipay/pagepay/buildermodel/AlipayTradePagePayContentBuilder.php';
require_once dirname(dirname(__DIR__)) . '/vendor/alipay/pagepay/service/AlipayTradeService.php';
class NoticeController extends Controller{
    public $enableCsrfValidation = false;
    public $layout=false; //重写这个属性就可以了   [yii2]不加载layout布局文件的实现方法
    public function behaviors()
    {
        return [
            'access' => [
                'class' => AccessControl::className(),
                'rules' => [
                    [
                        'actions' => ['login', 'error','view','alinotify'],
                        'allow' => true,
                    ],
                    [
                        'actions' => ['view','alinotify'],
                        'allow' => true,
                        'roles' => ['@'],
                    ],
                ],
            ],
        ];
    }
    /**
     * @inheritdoc
     */
    public function actions()
    {
        return [
            'error' => [
                'class' => 'yii\web\ErrorAction',
            ],
        ];
    }
    public  function actionAlinotify(){
        //获取回调参数，这里是以post传值
        $data=Yii::$app->request->post();
        //获取配置参数
        $config=Yii::$app->params['config2'];
        //实例化service对象
        $serviceobj= new \AlipayTradeService($config);
        //验证数据是否为支付宝返回
        $result=$serviceobj->check($data);
        if($result){
            //成功
            if($data['trade_status']=="TRADE_SUCCESS"){
//业务代码
    
            }
        }else{
            echo "fail";
        }
    }
}