public static function WeixinRequest($path, $body = '', $method = 'GET', $is_json = true)
{
    // 平台证书序列号
    if($path != '/v3/certificates')
    {
        $certificate = self::WeixinPlatformCertificate();
        if($certificate['code'] != 0)
        {
            return $certificate;
        }
    }
    // 请求签名+token
    $timestamp = strval(time());
    $nonce = strtoupper(RandomString(32));
    $body_json = empty($body) ? '' : json_encode($body, JSON_UNESCAPED_UNICODE);
    $message = $method."\n".$path."\n".$timestamp."\n".$nonce."\n".$body_json."\n";
    openssl_sign($message, $raw_sign, self::PrivateKey(), OPENSSL_ALGO_SHA256);
    $sign = base64_encode($raw_sign);
    $schema = 'WECHATPAY2-SHA256-RSA2048';
    $token = sprintf('mchid="%s",nonce_str="%s",timestamp="%d",serial_no="%s",signature="%s"', self::$config['weixin_merchant_id'], $nonce, $timestamp, self::$config['weixin_serial_no'], $sign);
    // 头信息
    $header = [
        'Content-Type: application/json',
        'Accept: application/json',
        'User-Agent: */*',
        'Authorization: '.$schema.' '.$token,
    ];
    // 非证书获取增加平台证书序列号
    if($path != '/v3/certificates')
    {
        $header[] = 'Wechatpay-Serial: '.$certificate['data']['serial_no'];
    }
    // 请求接口
    $url = 'https://api.mch.weixin.qq.com';
    $ret = CurlPost($url.$path, $body, 1, 30, $method, $header);
    if(!empty($ret['data']) && $is_json)
    {
        $ret['data'] = json_decode($ret['data'], true);
    }
    return $ret;
}

提示："{"code":"SIGN_ERROR","detail":{"detail":{"issue":"sign not match"},"field":"signature","location":"authorization","sign_information":{"method":"POST","sign_message_length":740,"truncated_sign_message":"POST\n/v3/fund-app/mch-transfer/transfer-bills\n1742393857\nRPSGCWSYNUFH7KMKCT9QXCNEXMXJUT4F\n{\"appid\"\n","url":"/v3/fund-app/mch-transfer/transfer-bills"}},"message":"错误的签名，验签失败"}"

怎么解决呢，求各位大咖指点下