I think this site uses 5 cookies.

PHPSESSID: This cookie is automatically created by PHP to store a key to your session data. All I did was use session_start() and the $_SESSION array.

sj_freepass: This one stores a long pass-code that is supposed to automatically log you in again if you had "Stylishly" checked. All I do is store the same code in the DB for your user account, and if it matches, you get logged in. I'm not sure if it is working, though.

sj_id: It stores your user_id number from the forum DB. I'm not sure what it's for actually. It might not do anything.

sj_timezone: Just to remember your time zone.

style: Stores whether you have the LIGHT or DARK style selected on the non-forum pages of SJcom.