How to perform signature verification on the content of WeChat payment result notification?

<code> ///验证签名
         $wx_sign = array();//微信给返回的数据加入一个数组做签名
         $wx_sign['appid']          = $wxdata['appid'];
         $wx_sign['bank_type']      = $wxdata['bank_type'];
         $wx_sign['cash_fee']       = $wxdata['cash_fee'];
         $wx_sign['fee_type']       = $wxdata['fee_type'];
         $wx_sign['is_subscribe']   = $wxdata['is_subscribe'];
         $wx_sign['mch_id']         = $wxdata['mch_id'];
         $wx_sign['nonce_str']      = $wxdata['nonce_str'];
         $wx_sign['openid']         = $wxdata['openid'];
         $wx_sign['out_trade_no']   = $wxdata['out_trade_no'];
         $wx_sign['result_code']    = $wxdata['result_code'];
         $wx_sign['return_code']    = $wxdata['return_code'];
         $wx_sign['time_end']       = $wxdata['time_end'];
         $wx_sign['total_fee']      = $wxdata['total_fee'];
         $wx_sign['trade_type']     = $wxdata['trade_type'];
         $wx_sign['transaction_id'] = $wxdata['transaction_id'];
         
         $wx_sign_all = $this->wechatAppPay->MakeSign($wx_sign);//调用签名函数</code>

<code>    /**
 * 生成签名
 *  @return 签名
 */
public function MakeSign( $params ){
    //签名步骤一：按字典序排序数组参数
    ksort($params);
    $string = $this->ToUrlParams($params);
    //签名步骤二：在string后加入KEY
    $string = $string . "&key=".$this->key;
    //签名步骤三：MD5加密
    $string = md5($string);
    //签名步骤四：所有字符转为大写
    $result = strtoupper($string);
    return $result;
}
</code>

<code> ///验证签名
         $wx_sign = array();//微信给返回的数据加入一个数组做签名
         $wx_sign['appid']          = $wxdata['appid'];
         $wx_sign['bank_type']      = $wxdata['bank_type'];
         $wx_sign['cash_fee']       = $wxdata['cash_fee'];
         $wx_sign['fee_type']       = $wxdata['fee_type'];
         $wx_sign['is_subscribe']   = $wxdata['is_subscribe'];
         $wx_sign['mch_id']         = $wxdata['mch_id'];
         $wx_sign['nonce_str']      = $wxdata['nonce_str'];
         $wx_sign['openid']         = $wxdata['openid'];
         $wx_sign['out_trade_no']   = $wxdata['out_trade_no'];
         $wx_sign['result_code']    = $wxdata['result_code'];
         $wx_sign['return_code']    = $wxdata['return_code'];
         $wx_sign['time_end']       = $wxdata['time_end'];
         $wx_sign['total_fee']      = $wxdata['total_fee'];
         $wx_sign['trade_type']     = $wxdata['trade_type'];
         $wx_sign['transaction_id'] = $wxdata['transaction_id'];
         
         $wx_sign_all = $this->wechatAppPay->MakeSign($wx_sign);//调用签名函数</code>

<code>    /**
 * 生成签名
 *  @return 签名
 */
public function MakeSign( $params ){
    //签名步骤一：按字典序排序数组参数
    ksort($params);
    $string = $this->ToUrlParams($params);
    //签名步骤二：在string后加入KEY
    $string = $string . "&key=".$this->key;
    //签名步骤三：MD5加密
    $string = md5($string);
    //签名步骤四：所有字符转为大写
    $result = strtoupper($string);
    return $result;
}
</code>