Any Ideas How To Read A Url That's Changed By The Server?

I apologize, but I posted this in the php general forum earlier and
realized that this is the more appropriate forum. Hopefully there's a
coder here who has done this in the past.

I've got code that uses CURL to go a web page to read the data.

When I type in www.website.com, the server automatically adds a
session variable to the url. I need to be able to read that session
variable. Then I will use that session variable to input into a new
CURL session.

Any ideas how I can do this?

If I use code like this:

// find out the domain:
$domain = $_SERVER['HTTP_HOST'];
// find out the path to the current file:
$path = $_SERVER['SCRIPT_NAME'];

It gives me the code for where my script is sitting on my server
rather than the values for the web site that I'm trying to read.

Any ideas?