php中文utf8字符截取--cmstop代码

function str_cutword($string,$length=80,$charset="utf-8",$etc='...')
{
        $start = 0;
        if (function_exists ("mb_substr" ))
            return mb_substr ( $string, $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], $string, $match );
        $slice = join ( "", array_slice ( $match [0], $start, $length ) );
        
        return $slice.$etc;
}