Hi.
The best way to deal with Japanese encoding (or any multi-byte codes) in PHP is to use mbstring extension. I believe there is a function(s) that converts among those Japanese encoding scheme, including the ones you are inquiring about. I assume you read Japanese:
PHP.net Manual mbstring
http://www.php.net/manual/ja/ref.mbstring.php
I believe it's bundled with PHP by default (ver.4.2x or later), but you must enable it when you compile PHP with
--enable-mbstring (and
--enable-mbstr-enc-trans if your PHP is earlier than 4.30 and
--enable-mbregex if you need Japanese regular expressions).
If you somehow can't do this (e.g. shared server, don't-know-how, etc), you can try
jcode.phps, which does not require any modification to your PHP setting:
http://www.spencernetwork.org/
Finally there are many articles written in Japanese that deal with Japanese encoding scheme in PHP, as well as the Japanese PHP communities (such as
http://www.php.gr.jp/ ) - you may want to check those out, too.
Good luck.