public function csubstr($str, $start=0, $length, $charset="utf-8", $suffix=true)  
    {  
        if(function_exists("mb_substr"))  
        {  
            if(mb_strlen($str, $charset) <= $length) return $str;  
            $slice = mb_substr($str, $start, $length, $charset);  
        } else {  
            $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, $match);  
            if(count($match[0]) <= $length) return $str;  
            $slice = join("",array_slice($match[0], $start, $length));  
        }  
        if($suffix) return $slice."…";  
        return $slice;  
    }