Is there a way to find out what file the user is viewing?

I'm hoping there is a fuction for this, its not a simple as as you might think. I have a set of files that the user can open, Say: index.php, request.php, staff.php, ect.... But when those files are opened they will all include the template.php file and inside this I want to beable to tell what the original file was entered. Also the template file sometimes includes files and I will need to still access the file name from these too.

I know I could do this with a variable in every file but I was wondering if there was a function that could do it?

Thanx