分割utf8中英混合字符串

/**
* @version $Id: str_split.php 10381 2008-06-01 03:35:53Z pasamio $
* @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];
}

$aaa = utf8_str_split("你好ABC");
echo '<pre>';
print_r($aaa);
echo '</pre>';
exit();