when I use extern.php like this

"extern.php?action=new&show=10"

there is some problem with multibyte charset

so I change

                $subject_truncated = pun_htmlspecialchars(trim(substr($cur_topic['subject'], 0, ($max_subject_length-5)))).' …';
to
                $subject_truncated = pun_htmlspecialchars(trim(mb_substr($cur_topic['subject'], 0, ($max_subject_length-5)))).' …';

and  problem was solved.

It's too hard to waiting..   T.T