You would need to set the cookie using the main domain and a path of "/".
If you have 3 subdomains:
fun.mydomain.com
shop.mydomain.com
members.mydomain.com
The cookie would need the domain "mydomain.com" with the path "/" to be used when setting. I haven't played with cookies in a long time (a good thing) lol but the last time I had been I was getting problems from Netscape (forget what version) because it didn't seem to pick up on "mydomain.com" but it did work when I used ".mydomain.com" for the main domain. (but the problems I seemed to have had with netscape could have just been me) LoL
The syntax for setting a cookie is as follows:
setcookie ( string name [, string value [, int expire [, string path [, string domain [, int secure]]]]])
By looking at this I *think it may be possible to just add your main domain into the cookie path, divided by a coma. Example:
$config['cookiepath'] = "/,mydomain.com";
I hope this works for you.
