/**
    * if $types is not empty and doesn't include '*' then reject files with extensions not listed in $types
    * process_upload override
    */
    public function process_upload($saveas_filename, $maxbytes, $types = '*', $savepath = '/', $itemid = 0,
            $license = null, $author = '', $overwriteexisting = false, $areamaxbytes = FILE_AREA_MAX_BYTES_UNLIMITED) {
        //types check
        if (
            !empty($types) and
            ((is_array($types) and !in_array('*', $types)) or $types != '*')
        ) {
            $elname = 'repo_upload_file';
            //valid check
            if (isset($_FILES[$elname]) and !empty($_FILES[$elname]['name'])) {
                $fileext = strtolower(pathinfo($_FILES[$elname]['name'], PATHINFO_EXTENSION));
                $allowedext = is_array($types) ? $types : array($types);
                foreach ($allowedext as $k => $v) { $allowedext[$k] = strtolower(pathinfo($v, PATHINFO_EXTENSION)); }
                //check extensions
                if (!in_array($fileext, $allowedext)) {
                    throw new moodle_exception('invalidfiletype', 'repository', '', get_mimetype_description(array('filename' => $_FILES[$elname]['name'])));
                }
            }
        }
        //call original
        return $this->process_upload_original($saveas_filename, $maxbytes, $types, $savepath, $itemid, $license, $author, $overwriteexisting, $areamaxbytes);
    }