how to get cookies from a different domain with php and javascript

Question

Suppose i have a cookie set in first.com say user. Now i want to read that cookie in second.com through javascript and ajax. But it is not working.I have got xmlHttp.status=0.

sample code

in the second domain readcookie.php file

var xmlHttp;
    function createXMLHttpRequest(){
        if(window.ActiveXObject)
            xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
        if(window.XMLHttpRequest)
            xmlHttp=new XMLHttpRequest();
    }
    function readcookie(){

        createXMLHttpRequest(); 
        xmlHttp.open("GET","http://www.first.com/cookie.php",true);
        xmlHttp.onreadystatechange=getcookie;
        xmlHttp.send(null);
    }
    function getcookie(){
        if(xmlHttp.readyState==4){
            if(xmlHttp.status==200){
                var reply=xmlHttp.responseText;
                if(reply){
                    alert(reply);
                }
            }
            else
                alert(xmlHttp.status);
        }
    }

in the first domain cookie.php file

if(isset($_COOKIE['user'])){
        echo $_COOKIE['user'];
    }
    else{
        setcookie('user','a2345',0);
        echo $_COOKIE['user'];
    }

Answer 1

You can't read cookies from another domain - end of.

The only way I can think of is to add some code to the 2nd domain that gets the cookies for you and then to place this in a page on the 1st domain, in an iframe.

You obviously need full access to both domains to be able to do this kind of thing.

Answer 2

Your problem is that browsers wont let javascript to access different domain. Add:

header('Content-type: text/html');    
header('Access-Control-Allow-Origin: *');   

lines to the beginning of cookie.php and it'll work. Still, you wont get the cookie (or at least in Chrome). I couldnt yet figure out why. It seems as if chrome creates a new session for the javascript and wont let that session access previous cookies. Like HttpOnly.