https://cjdx.shangmangs.com/api/Notify/notify 这个是回调地址

public function notify()
{
    $donationModel = new Donation();
    $zhengshuModel = new Zhengshu();
    //存储微信的回调
    $xml = file_get_contents("php://input");
    $arr = $this -> XmlToArr($xml);

    if(empty($arr['out_trade_no'])){
        exit;
    }
    $out_trade_no = $arr['out_trade_no'];
    $openid=$arr['openid'];//openid
    $sign=$arr['sign'];//校验码
    $total_fee=$arr['total_fee'];//订单金额
    $transaction_id=$arr['transaction_id'];//微信支付号

    //订单表有无
    $count=$donationModel->where("out_trade_no='".$out_trade_no."'")->count(); //判断有无订单

    $myfile = fopen("newfile.txt", "w") or die("Unable to open file!");
    $txt = $out_trade_no."\n";
    fwrite($myfile, $txt);
    $txt = $openid."\n";
    fwrite($myfile, $txt);
    $txt='count:'.$count;
    fwrite($myfile, $txt);
    fclose($myfile);

    if($count==1)
    {
        //这里是回调之后数据库操作

    }
    echo 'success';
}