substr扩展版：支持中文字符串截取

function d_substr($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;
}

　　

;