Codeigniter sessions across sub domains

Question

I have multiple subdomains and i\'m trying to use the sessions across subdomains.

http://example.com
http://subdomain.example.com

I have al

Answer 1

Only $config['cookie_domain'] part is required, $config['cookie_prefix'] is only to make things clean or you have some sub domain uses same domain but does not wanted to be shared.

Answer 2

From the following solution : Sharing sessions

Both the cookie_domain and cookie prefix has to be set

$config['cookie_domain'] = ".example.com";
$config['cookie_prefix'] = "example_";

Answer 3

first floor is right ,but does not clearly the reason

Reasons: from: https://ellislab.com/forums/viewthread/131851/#651233

CI’s session, like any other session mechanism, uses a cookie to identify the session. It’s is the cookie that should be available cross-domain.

For domain, you need to specify ‘.domain.com’, not ‘*.domain.com’.