<?
        function get_file_extension($filename) {
                global $allowed_extensions;
                foreach($allowed_extensions as $k=> $extension) {
                        if($k == count($allowed_extensions) - 1){
                                $pat_ext .= "(" . $extension . ")";
                        }
                        else{
                                $pat_ext .= "(" . $extension . ")|";
                        }
                }
                $pattern = "/^.+\.(" . $pat_ext . ")$/";
                if(preg_match($pattern, $filename, $ext)) {
                        return $ext[0][0];
                }
                else {
                        return false;
                }
        }

?>