nested include_once()

If I use include_once() to include these files in main.php: main.php --------- include_once('lib.php'); include_once('service.php'); --------- And file service.php also has a line in it: service.php ---------- include_once('lib.php'); ---------- Will lib.php get included twice or only _once() ? I am wondering because get_included_files() acts kind of 'strange' and does not display files included from included files. Damn recursion :) [OT] Is there a way to tail files that get read from a Linux filesystem. That could help me find out what gets included and when? Cheers Roko