Include if file exists?

Hi! Is there a ready to use PHP function for including ONLY if the file exists? I tried it like this: [main.php] include_once("lib.php"); ....later includeIf("somefile.php"); [lib.php] function includeIf($filename) { if (!file_exists($filename)) { include_once($filename); } } You see the problem. The somefile.php seems to be included in the wrong file. It should be included in the main.php instead of lib.php. How can i still have the function in lib.php but the file will be included in main.php Thanx in advance J