$_SERVER['SCRIPT_NAME']
$_SERVER['REQUEST_URI']
$_SERVER['PHP_SELF']
__FILE__

Have your pick :)

Or do you mean $_SERVER['HTTP_REFERER'] ?

I may not have explained my situation correctly...
I know that $_SERVER['SCRIPT_NAME'] will hold the name of the current page. I was just wondering if there were any other $_SERVER variables that would have the calling page.

I have two files... a header.php and a appointments_done.php the header file is called at the beginning of every page, but if the calling page is appointments_done.php I want a different version of header.php to display.

I was planning on doing a simple name check in my if statement. Like,
if ($_SERVER['HTTP_REFERER'] =='/staging/appointments_done.php'){
...}
If this does not work.... I am unsure why.

If I understand you correctly, then you probably want this in header.php:

if ($_SERVER['PHP_SELF'] =='/staging/appointments_done.php') { 
  // do things 
} else { 
  // do something else 
}

Thank you RonPK that solve my problem.