php change file encoding

change.php

<?php

$filename = "changeme.csv";
$handle = fopen($filename, "r");
$contents = fread($handle, filesize($filename));
fclose($handle);

if (!mb_check_encoding($contents, 'UTF-8')
    OR !($contents === mb_convert_encoding(mb_convert_encoding($contents, 'UTF-32', 'UTF-8' ), 'UTF-8', 'UTF-32'))) {

    $contents = mb_convert_encoding($contents, 'UTF-8');
}

$fp = fopen('changed.csv', 'w');
fwrite($fp, $contents);;
fclose($fp);

echo 'done!'.PHP_EOL;