Warning: filemtime() [function.filemtime]: stat failed for (...)

[pdedecker]

Code:

<?phpecho date("H", filemtime("http://192.168.2.20/vrtnieuws/nieuws280907.mp3"));?>

Output:

Warning: filemtime() [function.filemtime]: stat failed for http://192.168.2.20/vrtnieuws/nieuws280907.mp3 in /var/www/vrtnieuws/test.php on line 2

Why do I get this error while http://192.168.2.20/vrtnieuws/nieuws280907.mp3 does exist?Update: fixed by replacing

echo date("H", filemtime("http://192.168.2.20/vrtnieuws/nieuws280907.mp3"));

with

echo date("H", filemtime("nieuws280907.mp3"));