I just tested it on my system and it works correctly. If it's failing to work correctly for you, then my best guess is that the sql statement isn't returning the id. Try running that same query in the mysql cli (or phpmyadmin if you prefer) to verify that it returns what you expect.

Your choice to switch to using the server side sessions is good, but when you feel less frustrated, you should retry the cookie route just to learn how it should be done.