ajax call from pure javascript not returning response from remote php file(no jQuery)

Question

I am using pure javascript to make an ajax call to a PHP file which is residing in the remote server . But it is not returning the response.

The page which is making the ajax call is in my localhost .

Here is the ajax call code:

if (window.XMLHttpRequest) {
        xmlhttp=new XMLHttpRequest();
    }
    else{
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
    }
    xmlhttp.onreadystatechange=function(){
        if (xmlhttp.readyState==4 && xmlhttp.status==200){
            if(xmlhttp.responseText == 1){
                document.getElementById("update").innerHTML = "Update Successfull";
            }
        }
    }
    //https://flo2go-airteliptv.rhcloud.com
    xmlhttp.open("POST",'https://xyz.com/purchasereturn.php',true);
    xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlhttp.send("setflag=1");

The PHP code on the remote server is this:

<?php
header('content-type: application/javascript; charset=utf-8');
    $purchasevalue = 0;
    while($purchasevalue != 1){
        $query = "SELECT * FROM purchase WHERE purchase_id = 1";
        $result = mysql_query($query);
        while($row = mysql_fetch_array($result)){
            $purchasevalue = $row['purchase_flag'];
        }
    }
    //$purchasevalue = "{purchase:$purchasevalue}";
    echo $purchasevalue;
?>

How can I get the response ? Please help.

Answer 1

你为什么要问if(xmlhttp.responseText == 1){ xmlhttp.responseText是实际的响应，我看到你返回的是json，所以它永远不会返回1，所以永远不会进入if