Sessions is pretty easy in PHP to do. The subject is dicussed in the PHP Manual and in several books, as well as several Articles on this site are devoted to sessions.
I suggest that you get the PHP4 Bible written by Tim Converse and Joyce Park.
Many programmers on this site tend to SCREAM and YELL and CUSS at people that ask general questions like this, so I am going to be the nice guy here, and simply ask that you read up on the subject, test some scripts out and after that, Post on here with your questions.
Since I am already here, I will go ahead and try to give a primer (very Basic):
<b>TO START A PHP SESSION:</b>
session_start();
<b>YOU CAN REGISTER VARIABLES LIKE SO:</b>
session_register('Variable name goes here');
**note- you do not need to put a $ in front of the variable name.
PHP makes Sessions an easy proposition, so read up on it and try somethings out on your own. I have learned it is all trial and error, just keeping trying until something works, it is the best way to learn.