调用的接口：https://api.mch.weixin.qq.com/v3/refund/domestic/refunds；

退款代码（PHP）：

static public function tuikuan($money_fen,$total,$out_trade_no,$reason="协商退款"){
        $url = 'https://api.mch.weixin.qq.com/v3/refund/domestic/refunds';
        $data = [
            "out_trade_no"=>$out_trade_no,//商户订单号
            "out_refund_no"=>$out_trade_no,//商户退款单号
            "reason"=>$reason,//
            "notify_url"=>"https://api.huodongbaobao.com/pay/weixinpay_tuikuan_notify",//退款结果回调url
            "amount"=>[
                "refund"=>$money_fen,//退款金额，单位为分。示例值：100
                "total"=>$total,//原支付交易的订单总金额，单位为分。示例值：100
                "currency"=>"CNY"
            ],
        ];
        $header = [
            "Accept: application/json",
            "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36",
            self::getSign($url,json_encode($data)),
        ];
        $res = curl($url,$data,true,$header);
        if(!isset($res['body'])){
            return ["status"=>"error","msg"=>"微信申请退款请求失败"];
        }
        $data = json_decode($res['body'],true);
        if(
            isset($data['refund_id']) &&
            isset($data['status']) &&
            !empty($data['refund_id']) &&
            !empty($data['status']) 
        ){
            $res_status = $data['status'];//$data['status']枚举值：SUCCESS：退款成功 CLOSED：退款关闭 PROCESSING：退款处理中 ABNORMAL：退款异常
            if($res_status == "SUCCESS"){
                return ["status"=>"ok","data"=>"success"];
            }else if($res_status == "PROCESSING"){
                return ["status"=>"ok","data"=>"processing"];
            }else{
                return ["status"=>"error","msg"=>"退款异常"];
            }
        }
        $msg = isset($data['code']) ? $data['code'] : "";
        $msg .= isset($data['message']) ? "【".$data['message']."】" : "";
        return ["status"=>"error","msg"=>$msg];
    }

生成签名的代码：

    static private function getSign($url,$body,$http_method = "POST",$timestamp = 0,$nonce = ""){
        $url_parts = parse_url($url);
        $canonical_url = ($url_parts['path'] . (!empty($url_parts['query']) ? "?{$url_parts['query']}" : ""));
        if(empty($timestamp)){
            $timestamp = time();
        }
        if(empty($nonce)){
            $nonce = makeCode(32,true);
        }
        $message = $http_method."\n".$canonical_url."\n".$timestamp."\n".$nonce."\n".$body."\n";
        openssl_sign($message, $raw_sign, file_get_contents(config("app.weixin_mchid_api_cert_pem")), 'sha256WithRSAEncryption');
        $sign = base64_encode($raw_sign);
        $schema = 'WECHATPAY2-SHA256-RSA2048';
        $token = sprintf('mchid="%s",serial_no="%s",nonce_str="%s",timestamp="%d",signature="%s"',config("app.weixin_mchid"),config("app.weixin_mchid_api_cert_serial"),  $nonce, $timestamp, $sign);
        return "Authorization: " . $schema . " " . $token;
    }

入参：

(

    [out_trade_no] => 20250**********82541
    [out_refund_no] => 2025030**********541
    [reason] => 协商退款
    [notify_url] => https:/xx.yy.com/pay/weixinpay_tuikuan_notify
    [amount] => Array
        (
            [refund] => 1
            [total] => 1
            [currency] => CNY
        )
)
 

打印出的参数：

生成签名用的数据：
POST
/v3/refund/domestic/refunds
1742463956
evhvqt02e7b125wsuienffzt4bgzv7mt
{"out_trade_no":"20250309151620582541","out_refund_no":"20250309151620582541","reason":"\u534f\u5546\u9000\u6b3e","notify_url":"https:\/\/api.huodongbaobao.com\/pay\/weixinpay_tuikuan_notify","amount":{"refund":1,"total":1,"currency":"CNY"}}

生成的header Authorization：
Kimj2a4kl/A8zG/xtGG5RneTVRrHVBvkDaccFhK1NzXwP1GReutazJtdKXpOOXl6rtwx/ke4DzV8zmt8XHUunX/3wIPZ3DZrlV/F+xM9lX3um1VudL6yxLovB4djfcloO0QlzN8XzRhf1k9f25hvDiBgAMzZ9omNp06Xigpnjy2lgaTS/CpihjG2j+qKtHg0t/cIvVdfkYW59cX/t+XBRNBGozFpTm6OnxqnbCj/r90da1GQ20AZQMjYl3X4gWBIOqyBrCt5yJk2atFq/6fRA2Zc3cFzwSlTJjx11phIyGsrgG5X+JVosTW1eWGceDNGhoFy6vJmU6C8HSNWSW9kzQ==authorization-admin:
Authorization: WECHATPAY2-SHA256-RSA2048 mchid="165****008",serial_no="4498A82FCC548B7B4932AA4939807C395109770B",nonce_str="evhvqt02e7b125wsuienffzt4bgzv7mt",timestamp="1742463956",signature="Kimj2a4kl/A8zG/xtGG5RneTVRrHVBvkDaccFhK1NzXwP1GReutazJtdKXpOOXl6rtwx/ke4DzV8zmt8XHUunX/3wIPZ3DZrlV/F+xM9lX3um1VudL6yxLovB4djfcloO0QlzN8XzRhf1k9f25hvDiBgAMzZ9omNp06Xigpnjy2lgaTS/CpihjG2j+qKtHg0t/cIvVdfkYW59cX/t+XBRNBGozFpTm6OnxqnbCj/r90da1GQ20AZQMjYl3X4gWBIOqyBrCt5yJk2atFq/6fRA2Zc3cFzwSlTJjx11phIyGsrgG5X+JVosTW1eWGceDNGhoFy6vJmU6C8HSNWSW9kzQ=="
~                                                                                                                           

最终的问题：

调用微信退款接口后，微信返回内容打印如下：

Array
(
    [request_header] => POST /v3/refund/domestic/refunds HTTP/1.1
Host: api.mch.weixin.qq.com
Accept: application/json
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36
Authorization: WECHATPAY2-SHA256-RSA2048 mchid="16****008",serial_no="4498A82FCC548B7B4932AA4939807C395109770B",nonce_str="evhvqt02e7b125wsuienffzt4bgzv7mt",timestamp="1742463956",signature="Kimj2a4kl/A8zG/xtGG5RneTVRrHVBvkDaccFhK1NzXwP1GReutazJtdKXpOOXl6rtwx/ke4DzV8zmt8XHUunX/3wIPZ3DZrlV/F+xM9lX3um1VudL6yxLovB4djfcloO0QlzN8XzRhf1k9f25hvDiBgAMzZ9omNp06Xigpnjy2lgaTS/CpihjG2j+qKtHg0t/cIvVdfkYW59cX/t+XBRNBGozFpTm6OnxqnbCj/r90da1GQ20AZQMjYl3X4gWBIOqyBrCt5yJk2atFq/6fRA2Zc3cFzwSlTJjx11phIyGsrgG5X+JVosTW1eWGceDNGhoFy6vJmU6C8HSNWSW9kzQ=="
Content-Type: application/json; charset=utf-8
Content-Length:229
    [request_body] => {"out_trade_no":"20250309151620582541","out_refund_no":"20250309151620582541","reason":"协商退款","notify_url":"https:\/\/api.huodongbaobao.com\/pay\/weixinpay_tuikuan_notify","amount":{"refund":1,"total":1,"currency":"CNY"}}
    [header] => HTTP/1.1 401 Unauthorized
Server: nginx
Date: Thu, 20 Mar 2025 09:45:57 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 377
Connection: keep-alive
Keep-Alive: timeout=8
Cache-Control: no-cache, must-revalidate
X-Content-Type-Options: nosniff
Request-ID: 08D5C7EFBE061053189DDFEEA30620A8B50128DA38-269546525
Content-Language: zh-CN
    [body] => {"code":"SIGN_ERROR","detail":{"detail":{"issue":"sign not match"},"field":"signature","location":"authorization","sign_information":{"method":"POST","sign_message_length":307,"truncated_sign_message":"POST\n/v3/refund/domestic/refunds\n1742463956\nevhvqt02e7b125wsuienffzt4bgzv7mt\n{\"out_tr\n","url":"/v3/refund/domestic/refunds"}},"message":"错误的签名，验签失败"}
)

最下面的[body]中返回了报错信息：{"code":"SIGN_ERROR","detail":{"detail":{"issue":"sign not match"},"field":"signature","location":"authorization","sign_information":{"method":"POST","sign_message_length":307,"truncated_sign_message":"POST\n/v3/refund/domestic/refunds\n1742463956\nevhvqt02e7b125wsuienffzt4bgzv7mt\n{\"out_tr\n","url":"/v3/refund/domestic/refunds"}},"message":"错误的签名，验签失败"}

我小程序上有一个退款功能，电脑端管理后台也有一个退款功能，小程序端退款功能的代码和电脑端退款功能的代码是处于两个地方，但代码内容是一模一样的（复制的），二者使用的是同一套证书、密钥，小程序上的支付、退款功能都好用，但电脑端的退款功能就不好用，请求退款接口时提示上面的报错内容，调试了很久，确实没找到问题原因，请大家帮忙看看。