(possibly) dumb question about passing cookies between subdomains

One of the sites I run has a login page on a different subdomain from the rest of the site. Let’s say, for the sake of discussion, that the login page is here:

http://registration.foo.com

and the rest of the content’s all here:

http://foo.bar.foo.com

I need something on the main site (a poll) to recognize the username, and the only way I can possibly do this with what I have available is to set a cookie on the login page, and retrieve it in the main site.

On the login page, I have tried this:

and this:

Neither of these work. Is there something I’ve forgotten about the way cookies set in one subdomain of foo.com can be readable in another? Or a dumb mistake? Or (uh oh) can it just not be done with the situation I’ve got here?

And no, I can’t do this with server-side scripting in this case…

I think it needs to be .foo.com. (Leading dot.) But I haven’t done cookie stuff for a while, so I may be remembering wrong.

Nope, that’s not quite it… tried that and it’s still not going through. There must be a way as cookies from all over the .foo domain are showing up… so I guess best bet is to take a look at some of these pages and see what they’re doing differently. Will post what I find out.

Sorry to take so long to try this and get back on it… was forced to back-burner this for a few days.

Actually it is a leading dot, but it will only work between the same levels within the domain name.

By setting the cookies domain to .mysite.com, you can share cookies between:
register.mysite.com
www.mysite.com
frank.mysite.com
jimbo.mysite.com

But the cookies will not be shared with
mysite.com
or
anne.frank.mysite.com
jumbo.jimbo.mysite.com

The domain level must be equal to share cookies.

Dang… I was afraid that might be what was going wrong. Looks like I’m SOL.

Thanks for letting me know, though!

You could perhaps just carry the username over via a query string to your desired url, and then if that query string exists set a cookie in the next domain.

For example, you could set the cookie username on the register.foo.com domain, and within any page in the register domain or any other *.foo.com domain, you could get the cookie, and append it to the links URLS. eg


http://foo.bar.foo.com?username=COOKIE_USERNAME_VAL

Then once in the subdomain you can get the value from the query string via javascript and set the new cookie in foo.bar.foo.com.