php-iconv-sjis.php

<?php
$file = fopen('utf8.txt', 'r');
$content = fread($file, filesize('utf8.txt'));
$converted_content = mb_convert_encoding($content, 'SJIS', 'UTF-8');

echo $converted_content;

$fp = fopen('sjis.txt', 'w');
fwrite($fp, $converted_content);
fclose($fp);