Multiple domain cookie

[Anon]

Hi
I´m studing the university and I have a project where i need give a solution:
we have 4 domain wwww.com
xxxx.com
yyyy.com
zzzz.com
and I want that a unique cookie is doing written for any of four domains and could be read for any of four domains.

Similar to doubleclick.com do it.

Is it possible that cookie could be read by different domain whose was writte?
Do you know if exist some option in the cookie parameter (domain) it could be read for multiple domains?
Could you please give me some reference to sites, peoples about this subjet.

thanks in advance

[e-mail]

[Anon]

You can't send a single cookie that is valid across multiple domains.

Doubleclick doesn't. It sends cookies that are valid in its own domain.

Keep in mind that Doubleclick is serving the ad graphics. Therein lies the key.