I use these regular expressions all the time, but it’s much more convenient to have them both in convenient PHP functions.
// Returns only the file extension (without the period).
function file_ext($filename) {
if( !preg_match('/\./', $filename) ) return '';
return preg_replace('/^.*\./', '', $filename);
}
// Returns the file name, less the extension.
function file_ext_strip($filename){
return preg_replace('/\.[^.]*$/', '', $filename);
}


Very handy, and much more elegant than the ‘traditional’ explode() / strstr() / substr() etc. methods.
Nice one. I just started working with Regex in PHP and this has definitely come in very handy.