I do not have register_globals turned on, and the sessions work file. Perhaps the article you were reading is wrong?
Since you are new to PHP, perhaps a good idea might be to look over other peoples code instead of trying to jump in and design your own applications at first. Places like http://www.hotscripts.com/
have code that people have written that you can download and look at. Keep in mind you will come across some pretty crappy code examples, but it might prove to be a good place to start learning php. Also check out http://www.php.net
for documentation on php and mysql.
I think wizard posted a post that describes the global variables: http://www.php-forum.com/p/viewtopic.php?t=2181