CORS not working php

I am trying to post form data from www.siteone.com to www.sitetwo.com via CORS. My ajax code is this:

<script>
$(document).ready(function(){
        $("#submit").live('click',function() {
            var url = "http://www.sitetwo.com/cors.php";
            var data = $('#form').serialize();
            jQuery.ajax({
                url : url,
                type: "POST",
                data : $('#form').serialize(),
                }).done(function(response){
                    alert(response);
                    }).fail(function(error){
                    console.log(error.statusText);
                    });
                return false;


});
});
</script>

and the file cors.php in www.sitetwo.com is as follows:

<?php
 header('Access-Control-Allow-Origin: *');
 header('Access-Control-Allow-Methods: POST, GET, OPTIONS');
 echo "hai";
?>

But still Access-control-Allow-Origin error is thrown. The error thrown is this:

XMLHttpRequest cannot load http://www.sitetwo.com/cors.php. Origin http://www.siteone.com is not allowed by Access-Control-Allow-Origin. 

I came to know that, using CORS by just allowing the remote website via headers, we can use cross-domain request. But when I tried like this, error is thrown. Have I missed anything in here? Here is my request/response headers:

Response Headers
Connection  Keep-Alive
Content-Length  487
Content-Type    text/html; charset=iso-8859-1
Date    Fri, 23 Aug 2013 05:53:20 GMT
Keep-Alive  timeout=15, max=99
Server  Apache/2.2.15 (CentOS)
WWW-Authenticate    Basic realm="Site two Server - Restricted Area"
Request Headers
Accept  */*
Accept-Encoding gzip, deflate
Accept-Language en-US,en;q=0.5
Content-Length  43
Content-Type    application/x-www-form-urlencoded; charset=UTF-8
Host    www.sitetwo.com
Origin  http://www.siteone.com
Referer http://www.siteone.com/index.html
User-Agent  Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:23.0) Gecko/20100101 Firefox/23.0

Answer

Finally, I myself have solved the problem explained in the question. The code that I have implemented for accessing header is incorrect.

The below mentioned two line code, when given, didn’t work:

<?php
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: POST, GET, OPTIONS');
?>

But handling CORS requests properly is a tad more involved. Here is a function that will respond more fully. The updated code is this :

 <?php
    // Allow from any origin
    if (isset($_SERVER['HTTP_ORIGIN'])) {
        header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
        header('Access-Control-Allow-Credentials: true');
        header('Access-Control-Max-Age: 86400');    // cache for 1 day
    }

    // Access-Control headers are received during OPTIONS requests
    if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {

        if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
            header("Access-Control-Allow-Methods: GET, POST, OPTIONS");         

        if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
            header("Access-Control-Allow-Headers:        {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");

        exit(0);
    }

    echo "You have CORS!";
?>

I have found from another post It worked….