php对接支付宝支付退款功能，亲测可行

<?php
require_once '../extend/alipay/aop/AopClient.php';
require_once '../extend/alipay/aop/AopCertClient.php';
require_once '../extend/alipay/aop/AopCertification.php';
require_once '../extend/alipay/aop/AlipayConfig.php';
require_once '../extend/alipay/aop/request/AlipayTradeRefundRequest.php';

/**
 * 支付宝服务类
 * 封装支付宝相关功能，包含完整默认配置，适合单一支付宝账号的项目
 */
class Alipay
{

    private $aop;

    public function __construct() {
        $config = get_addon_config('epay');//这里我用的fasadmin的插件配置,可自己修改为普通数据存储配置
        $this->aop = new AopClient();
        $this->aop->gatewayUrl = 'https://openapi.alipay.com/gateway.do';
        $this->aop->appId = $config['alipay']['app_id'];
        $this->aop->rsaPrivateKey = $config['alipay']['private_key'];
        $this->aop->alipayrsaPublicKey = $config['alipay']['ali_public_key'];
        $this->aop->signType = 'RSA2';
        $this->aop->postCharset = 'UTF-8';
        $this->aop->format = 'json';
    }

    /**
     * 支付宝退货处理
     * 退货前提是必须支付成功
     * @param type $orderId
     * @return bool
     */
    public function refund($params) {
        $request = new AlipayTradeRefundRequest ();
        $bizcontent = json_encode([
            //'out_trade_no'=>$params['out_trade_no'],
            'trade_no'=>$params['trade_no'],
            'refund_amount'=>$params['refund_amount'],
            'refund_reason'=>'正常退款'
        ]);
        $request->setBizContent($bizcontent);
        $result = $this->aop->execute($request);
        $responseNode = str_replace(".", "_", $request->getApiMethodName()) . "_response";
        $resultCode = $result->$responseNode->code;
        //var_dump($result->$responseNode);
        if(!empty($resultCode)&&$resultCode == 10000){//退款成功
             $result=[
                'trade_no'=>$result->$responseNode->trade_no,
                'out_trade_no' =>$result->$responseNode->out_trade_no,
             ];
             return $result;
        } else {//退款失败
            return false;
        }
    }
}
?>

//测试支付宝退款
    public function test_alipay_refund(){
        $order_id=$this->request->param('order_id');//订单id
        $option['id']=$order_id;
        $order=Db::name('hospital_order')->where($option)->find();
        if(!$order){
            $this->error('该订单不存在');
        }
        $alipay = new \Alipay();
        $out_refund_no='tk_'.create_order_sn();
        $params=[
          //'out_trade_no' => '商户订单号（与trade_no二选一）',
          'trade_no' => $order['trade_no'],
          'refund_amount' => $order['pay_amount'],
          'refund_reason' => '正常退款',
          'out_request_no' => $out_refund_no,
          //'refund_goods_detail' =>[],
          //'refund_royalty_parameters' => [],退分账明细信息
          //'query_options' => '查询选项',
          //'related_settle_confirm_no' => '针对账期交易'
        ];
        $result=$alipay->refund($params);
        var_dump($result);die;
    }