I figure most people will want a simple way to break-up a multibyte string into its individual characters. Here's a function I'm using to do that. Change UTF-8 to your chosen encoding method.

<?php
function mbStringToArray ($string) {
    $strlen = mb_strlen($string);
    while ($strlen) {
        $array[] = mb_substr($string,0,1,"UTF-8");
        $string = mb_substr($string,1,$strlen,"UTF-8");
        $strlen = mb_strlen($string);
    }
    return $array;
}
?>