When should I use session variables instead of cookies?

Question

Session variables and cookies seem very similar to me. I understand the technical differences, but how do you decide when to use one vs. the other?

Answer 1

Sessions are stored on the server side. If a visitor stores something in a cookie, the browser will send the user information for every request made.

This tends to consume a lot of servers computer time and slowing the user's experience. Some browsers also do not support cookies giving more advantage to sessions over cookies... I strongly recommend sessions.

This might help: Cookies (php.net)