$_SERVER['PHP_SELF'] in a included file

A project that I work on has a index.php that includes other files depending on certain requirements. so index.php includes a.php; in a.php if you echo $_SERVER['PHP_SELF'] it echos index.php and I understand why it does this. But, I want echo the file name of a.php from a.php and I dont want to add a $filename='a.php'; at the top of a.php, although I have thought of using subversion and a find and replace to insert $filename="$Id$"; at the top of all the files. Does anyone know know of another way I can get a included files filename? Sorry if I have posted this question in the past, its been a while since I last thought of this problem. Regards, Clive. Real Time Travel Connections {No electrons were harmed in the creation, transmission or reading of this email. However, many were excited and some may well have enjoyed the experience.}