case 'encodeheader':
            $result = '';
            if (strlen($ret) > 0) {
                $tmpstr = mb_substr($ret, 0, 1);
                $prevcsize = strlen($tmpstr);
                for ($i = 1; $i < mb_strlen($ret); $i++) {
                    $tmp = mb_substr($ret, $i, 1);
                    if (strlen($tmp) == $prevcsize) {
                        $tmpstr .= $tmp;
                    } else {
                        if ($prevcsize == 1) {
// mistake, two atoms combined without space
                            $result .= $tmpstr;
                        } else {
                            $result .= str_replace(' ', '',
                                                   mb_encode_mimeheader($tmpstr,'iso-2022-jp','B',''));
                        }
                        $tmpstr = $tmp;
                        $prevcsize = strlen($tmp);
                    }
                }
                if (strlen($tmpstr)) {
                    if (strlen(mb_substr($tmpstr, 0, 1)) == 1)
// two atoms combined without space
                        $result .= $tmpstr;
                    else
                        $result .= str_replace(' ', '',
                                               mb_encode_mimeheader($tmpstr,'iso-2022-jp','B',''));
                }
            }
            $ret = $result;
            break;
        case 'decodeheader':