public/js/kcfinder/lib/helper_file.php
static function getExtension($filename, $toLower=true) {
        return preg_match('/^.*\.([^\.]*)$/s', $filename, $patt)
            ? ($toLower ? strtolower($patt[1]) : $patt[1]) : "";
    }
static function getExtension($filename, $toLower=true) {
        return preg_match('/^.*\.([^\.]*)$/s', $filename, $patt)
            ? ($toLower ? strtolower($patt[1]) : $patt[1]) : "";
    }
Get the extension from filename
@param string $filename
@param bool $toLower
@return string