How to check if a .swf exists

error checking

[StoutFiles]

I pass a GET variable to call my swf's with php. If a .swf doesn't exist, is there anyway I can know this and redirect to an error page or display an error message instead of a blank box where a flash file should be?

[rocknbil]

var $flash = '/full/path/to/swf/dir/' . $_GET['f']; // Cleanse!

if (is_file($flash)) { // display it }
else { // alt content }

Something like that?

[StoutFiles]

That worked perfectly! Thank you.