Receiving AJAX HTTP Response Code as 0

Question

I have a pretty simple AJAX and PHP code. While calling the PHP through the AJAX it receives the response code as 0. The PHP code is successfully run, but I can't get the response. What does this status '0' denote and how can I solve this?

function confirmUser(id)
{
    xmlhttp=GetXmlHttpObject();
    regid = id;
    if (xmlhttp==null)  {
        alert ("Browser does not support HTTP Request");
        return;
    }
    var url="confirm.php";
    url=url+"?id="+id;
    url=url+"&a=confirm";
    xmlhttp.onreadystatechange=function() {
        if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
            $("#txtHint" + regid).text("Awaiting confirmation");
        } else {
            alert (xmlhttp.status); //this shows '0'
        }
    };
    xmlhttp.open("GET",url,true);
    xmlhttp.send(null);
}

Well, this is the javascript I used. Pardon me if I should've added anything more than this. Also tell me what I missed. I appreciate your help

GetXmlHttpObject function:

function GetXmlHttpObject()
{
    if (window.XMLHttpRequest) {
        // code for IE7+, Firefox, Chrome, Opera, Safari
        return new XMLHttpRequest();
    }
    if (window.ActiveXObject) {
        // code for IE6, IE5
        return new ActiveXObject("Microsoft.XMLHTTP");
    }
    return null;
}

Answer 1

When working with XMLHttpRequests in the past, I've found that status 0 is usually returned for locally processed files. When I saw this question, I had a bit of a hunt around and found a confirmation of this at the following pages:

• XMLHttpRequest - Why Status 0, and StatusText Unknown occur
• https://developer.mozilla.org/En/Using_XMLHttpRequest#section_3

Answer 2

Here are the readyState codes for you.

0. Uninitialized
1. Set up, but not sent
2. Sent
3. In flight
4. Complete

(Source: http://www.stevefenton.co.uk/Content/Blog/Date/201004/Blog/AJAX-Ready-State-Codes/)

Do you get stuck constantly on a readyState of 0? If so, it means your request hasn't been sent, although I can see a line of code in your example "xmlhttp.send(null)"...

I would predict that you'll get a 0 before you call send, but after that a different status code. What happens if you wait a bit?