Access cookie of parent domain

[NotionCommotion]

I expected the following script to display a single cookie on the main page (cookie_2, and both the main page cookie and the subdomain cookie (cookie_3) within the iframe.

 

In actuality, the main page was as expected, but the iframe only displays cookie_3.

 

Can anyone explain what I am witnessing, and why the subdomain wouldn't be able to access the cookie set in the parent?

<?php
setcookie("cookie_".count(explode('.', $_SERVER['HTTP_HOST'])), 'Hello from '.$_SERVER['HTTP_HOST']);
echo('<pre>'.print_r($_COOKIE,1).'</pre>');
?>

<iframe src="http://test.mysite.com/testing/cookietest.php"></iframe>

[kicken]

Try setting the domain parameter of the cookie as well to your base domain name. According to the RFC for cookies:

If the server omits the Domain attribute, the user agent will return the cookie only to the origin server

[NotionCommotion]

Thanks Kicken,  I had just stumbled upon this and am starting to experiment.