<?php
/* Convert internal character encoding to SJIS */
$str = mb_convert_encoding($str, "SJIS");
/* Convert EUC-JP to UTF-8 */
$str = mb_convert_encoding($str, "UTF-8", "EUC-JP");
/* Auto detect encoding from JIS, eucjp-win, sjis-win, then convert str to UCS-2LE */
$str = mb_convert_encoding($str, "UCS-2LE", "JIS, eucjp-win, sjis-win");
/* "auto" is expanded to "ASCII,JIS,UTF-8,EUC-JP,SJIS" */
$str = mb_convert_encoding($str, "EUC-JP", "auto");
?>
Just look at those conversions go !
=)