Cookie of different domains in PHP

Question

is it possible to access cookie of a domain foo.com in another domain like example.com using php?

Answer 1

No, it is not possible, cookie is assigned only to domain it was set. You can access it only if domain foo.com send somehow its cookie data to other domain.

Answer 2

It has nothing to do with PHP, this is a browser security setup. By default, it is not allowed. The reasons should be obvious. I wouldn't want anyone to be able to read all my cookies.

However, you can setup something using a cross domain communication channel. This requires the target domain to grant access to the source domain to read cookies. This is how Facebook Connect works. This generally involved iframes and javascript on the client side, but the cookie value could be passed to PHP.

Here is a write up from MS on the topic. http://msdn.microsoft.com/en-us/library/bb735305.aspx

Answer 3

Try searching on Stack Overflow for 'SSO' for details of how to implement sessions / authentication spanning domains.

C.