Check if cookies are enabled

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I am working on a page that requires javascript and sessions. I already have code to warn the user if javascript is disabled. Now, I want to handle the case where cookies are disabled, as the session id is stored in cookies.

I have thought of just a couple ideas:

  1. Embedding the session id in the links and forms
  2. Warn the user they must enable cookies if they are disabled (would need help detecting if cookies are disabled)

What is the best way to approach this? Thanks

EDIT

Based on the articles linked, I came up with my own approach and thought I would share, somebody else might be able to use it, maybe I will get a few critiques. (Assumes your PHP session stores in a cookie named PHPSESSID)

<div id="form" style="display:none">Content goes here</div>
<noscript>Sorry, but Javascript is required</noscript>
<script type="text/javascript"><!--
if(document.cookie.indexOf('PHPSESSID')!=-1)
   document.getElementById('form').style.display='';
else
   document.write('<p>Sorry, but cookies must be enabled</p>');
--></script>


JavaScript

In JavaScript you simple test for the cookieEnabled property, which is supported in all major browsers. If you deal with an older browser, you can set a cookie and check if it exists. (borrowed from Modernizer):

if (navigator.cookieEnabled) return true;

// set and read cookie
document.cookie = "cookietest=1";
var ret = document.cookie.indexOf("cookietest=") != -1;

// delete cookie
document.cookie = "cookietest=1; expires=Thu, 01-Jan-1970 00:00:01 GMT";

return ret;

PHP

In PHP it is rather "complicated" since you have to refresh the page or redirect to another script. Here I will use two scripts:

somescript.php

<?php
session_start();
setcookie('foo', 'bar', time()+3600);
header("location: check.php");

check.php

<?php echo (isset($_COOKIE['foo']) && $_COOKIE['foo']=='bar') ? 'enabled' : 'disabled';