php中文字串截取无乱码的方法

echo mb_substr('我们都是好孩子hehe',0,9);
?>

function msubstr($str, $start=0, $length, $charset="utf-8", $suffix=true)
    {
        if(function_exists("mb_substr"))
            return mb_substr($str, $start, $length, $charset);
        elseif(function_exists('iconv_substr')) {
            return iconv_substr($str,$start,$length,$charset);
        }
        $re['utf-8']   = "/[x01-x7f]|[xc2-xdf][x80-xbf]|[xe0-xef][x80-xbf]{2}|[xf0-xff][x80-xbf]{3}/";
        $re['gb2312'] = "/[x01-x7f]|[xb0-xf7][xa0-xfe]/";
        $re['gbk']    = "/[x01-x7f]|[x81-xfe][x40-xfe]/";
        $re['big5']   = "/[x01-x7f]|[x81-xfe]([x40-x7e]|xa1-xfe])/";
        preg_match_all($re[$charset], $str, $match);
        $slice = join("",array_slice($match[0], $start, $length));
        if($suffix) return $slice."…";
        return $slice;
    }