使用服务器端时间的javascript倒计时

<?php
$date = 'July 19 2011 05:00:00 PM PDT';
$exp_date = "var end = new Date('". $date ."');";
$todays_date = date("F j Y g:i:s A T");
if ($todays_date < $exp_date) {
?>
<script>
<?php echo $exp_date ;?>
var _second = 1000;
var _minute = _second * 60;
var _hour = _minute * 60;
var _day = _hour *24
var timer;
function showRemaining()
{
    var now = new Date();
    var distance = end - now;
    if (distance < 0 ) {
       clearInterval( timer );
       document.getElementById('countdown').innerHTML = 'EXPIRED!';
       return;
    }
    var days = Math.floor(distance / _day);
    var hours = Math.floor( (distance % _day ) / _hour );
    var minutes = Math.floor( (distance % _hour) / _minute );
    var seconds = Math.floor( (distance % _minute) / _second );
    document.getElementById('countdown').innerHTML = 'Days: ' + days + '<br />';
    document.getElementById('countdown').innerHTML += 'Hours: ' + hours+ '<br />';
    document.getElementById('countdown').innerHTML += 'Minutes: ' + minutes+ '<br />';
    document.getElementById('countdown').innerHTML += 'Seconds: ' + seconds+ '<br />';
}
timer = setInterval(showRemaining, 1000);
</script>
<?php
} else {
    echo "Times Up";
}
?>
<div id="countdown"></div>

您应该向客户端提供当前时间和结束时间，因为客户端使用自己的系统时间来代替服务器的时间。

以下是这个问题的全部解决方案。

<?php
$date = 'July 20 2011 05:00:00 PM PDT';
$exp_date = strtotime($date);
$now = time();
if ($now < $exp_date) {
?>
<script>
// Count down milliseconds = server_end - server_now = client_end - client_now
var server_end = <?php echo $exp_date; ?> * 1000;
var server_now = <?php echo time(); ?> * 1000;
var client_now = new Date().getTime();
var end = server_end - server_now + client_now; // this is the real end time
var _second = 1000;
var _minute = _second * 60;
var _hour = _minute * 60;
var _day = _hour *24
var timer;
function showRemaining()
{
    var now = new Date();
    var distance = end - now;
    if (distance < 0 ) {
       clearInterval( timer );
       document.getElementById('countdown').innerHTML = 'EXPIRED!';
       return;
    }
    var days = Math.floor(distance / _day);
    var hours = Math.floor( (distance % _day ) / _hour );
    var minutes = Math.floor( (distance % _hour) / _minute );
    var seconds = Math.floor( (distance % _minute) / _second );
    var countdown = document.getElementById('countdown');
    countdown.innerHTML = '';
    if (days) {
        countdown.innerHTML += 'Days: ' + days + '<br />';
    }
    countdown.innerHTML += 'Hours: ' + hours+ '<br />';
    countdown.innerHTML += 'Minutes: ' + minutes+ '<br />';
    countdown.innerHTML += 'Seconds: ' + seconds+ '<br />';
}
timer = setInterval(showRemaining, 1000);
</script>
<?php
} else {
    echo "Times Up";
}
?>
<div id="countdown"></div>

我对@Ghostoy的var distance = end - now; 有问题

我注意到我倒计时的秒数经常会暂停，每隔一段时间就会跳过一个数字。当我显示距离时，我注意到毫秒有点来回移动。

例如，当我观看距离倒计时时，以下是我的结果：

400996000
400995001
400993998
400993002
400991999

可能只是我的电脑，但如果问题发生在我的电脑上，那么它可能发生在其他人身上。因此，我建议将var距离更改为：

var distance = Math.round((end - now)/1000)*1000;

这把它固定在我的机器上。

var end = new Date(<?php echo """.$todays_date." PDT""; ?>); // set expiry date and time..