CORS not working php

Question

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 1

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....

Answer 2

To allow CORS for all:

<?php
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept');

echo "You have CORS!";

Answer 3

Another reason is if you're missing a semicolon or something anywhere in your php, that CORS error message will be the only error that is displayed by the ajax, even if error reporting is on, while you can see the actual error by going to the php url in your browser.