php str_split 解决中文

<?php
/**
* @version $Id: str_split.php 
* @package utf8
* @subpackage strings
*/
function utf8_str_split($str, $split_len = 1)
{
    if (!preg_match('/^[0-9]+$/', $split_len) || $split_len < 1)
        return FALSE;
 
    $len = mb_strlen($str, 'UTF-8');
    if ($len <= $split_len)
        return array($str);
 
    preg_match_all('/.{'.$split_len.'}|[^\x00]{1,'.$split_len.'}$/us', $str, $ar);
 
    return $ar[0];
}
?>