实时功能

我已经设置了我的Agotime函数。我只是想知道我应该使用什么方法来让我的时间更新。很多人会说Ajax，但这会是服务器繁重吗？我需要每 5 秒平稳更换一次。

另外我该怎么做？

 function Agotime($date)
    {
        if(empty($date)) {
            return "No date provided";
        }
        $periods         = array("second", "minute", "hour", "day", "week", "month", "year", "decade");
        $lengths         = array("60","60","24","7","4.35","12","10");
        $now             = time();
        $unix_date       = strtotime($date);
           // check validity of date
        if(empty($unix_date)) {    
            return "Bad date";
        }
        // is it future date or past date
        if($now > $unix_date) {    
            $difference     = $now - $unix_date;
            $tense         = "ago";
        } else {
            $difference     = $unix_date - $now;
            $tense         = "from now";
        }
        for($j = 0; $difference >= $lengths[$j] && $j < count($lengths)-1; $j++) {
            $difference /= $lengths[$j];
        }
        $difference = round($difference);
        if($difference != 1) {
            $periods[$j].= "s";
        }
        return "$difference $periods[$j] {$tense}";
    }