How do I use cookies across two different domains?

Question

I need to share SSO information between two different domains with a cookie, can this be done in PHP and how?

Answer 1

I'm not sure about the security implications, but there is an Apache setting that allows you to change the domain of a cookie.

# in httpd.conf (or equivalent)
php_value session.cookie_domain mydomain.com

I have successfuly employed this method for subdomains, but have never attempted for different domains.

There is also a method to set the variables direction in PHP described at http://us.php.net/manual/en/function.session-set-cookie-params.php. The documentation makes no reference to the ability or inability to set cookies on a different domain.

There is a different Stack Overflow thread on this same topic, but I don't think it was ever sufficiently answered.