Sometimes it is not as straightforward
as one may think to get the current
url to use it inside your application.
Here is a snippet that I use to fetch
the current URL and use it in a
script. The current url (whether http
or https) is now a local variable that
you can do with as you please.

$url = "http".(!empty($_SERVER['HTTPS'])?"s":"").
"://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI'];

Note: You should groom this value before using in anything sensitive,like a sql query.