public function refound(){
        $ref= md5("appid=1233213&mch_id=1233213&nonce_str=2194kfhaafaf384&op_user_id=1461000002"
            . "&out_refund_no=201704181551358393&out_trade_no=201704181551358393&refund_fee=1&total_fee=1"
            . "&key=yudsd7rfer7dsadh0UfdoReraRdsad4d");//sign加密MD5
        $refund=array(
            ‘appid‘=>‘12323123‘,
            ‘mch_id‘=>‘123213213‘,//商户号
            ‘nonce_str‘=>‘2194kfhaafaf384‘,//随机字符串
            ‘op_user_id‘=>‘1461000002‘,
            ‘out_refund_no‘=>‘201704181551358393‘,
            ‘out_trade_no‘=>‘201704181551358393‘,
            ‘refund_fee‘=>‘1‘,
            ‘total_fee‘=>‘1‘,
            ‘sign‘=>$ref
        );
        $url="https://api.mch.weixin.qq.com/secapi/pay/refund";;//微信退款地址，post请求
        $xml=ToXml($refund);
        $ch=curl_init();
        curl_setopt($ch,CURLOPT_URL,$url);
        curl_setopt($ch,CURLOPT_HEADER,1);
        curl_setopt($ch,CURLOPT_RETURNTRANSFER,1);
        curl_setopt($ch,CURLOPT_SSL_VERIFYPEER,1);//证书检查
        curl_setopt($ch,CURLOPT_SSLCERTTYPE,‘pem‘);
        curl_setopt($ch,CURLOPT_SSLCERT,‘plugins/payment/weixin/cert/apiclient_cert.pem‘);
        curl_setopt($ch,CURLOPT_SSLCERTTYPE,‘pem‘);
        curl_setopt($ch,CURLOPT_SSLKEY,‘plugins/payment/weixin/cert/apiclient_key.pem‘);
        curl_setopt($ch,CURLOPT_POST,1);
        curl_setopt($ch,CURLOPT_POSTFIELDS,$xml);
        $data=curl_exec($ch);
        if($data){ //返回来的是xml格式需要转换成数组再提取值，用来做更新
            curl_close($ch);
            dump($data);
        }else{
            $error=curl_errno($ch);
            echo "curl出错，错误代码：$error"."<br/>";
            echo "<a href=http://www.mamicode.com/‘http://curl.haxx.se/libcurl/c/libcurs.html‘>;错误原因查询
";
            curl_close($ch);
            echo false;
        }
    }
   

function ToXml($arr)
{
    if(!is_array($arr)
        || count($arr) <= 0)
    {
        throw new WxPayException("数组数据异常！");
    }

    $xml = "<xml>";
    foreach ($arr as $key=>$val)
    {
        if (is_numeric($val)){
            $xml.="<".$key.">".$val."</".$key.">";
        }else{
            $xml.="<".$key."><![CDATA[".$val."]]></".$key.">";
        }
    }
    $xml.="</xml>";
    return $xml;
}