passing variables in PHP3

Hi,

I've written an application for the web that asks users for their
id and password, checks the database and if they are legit
takes them to a page. Now I'm using the PHP_AUTH_USER variable
to identify the user and I need that information from one
file to another. How do I do that ? I tried storing it in a
variable and sending it along an with html anchor but that is
not a neat way of doing it since every time I need the value of
that variable the user has to click on an image and another problem
with that is the user id will show up in the url and I don't want
that security risk.
So my question is how do I store the value of PHP_AUTH_USER for
a specific user and access it from many PHP3 files ?

I know most of you are PostgreSQL specialists but I was hoping
someone is familiar with this since its holding me up.
Thank you for any replies.
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