countdown php jquery post ajax - php

Question

I'm designing a website where there is a little game going on. Each user that participates has 99 minutes to complete it otherwise we display a game over state. Here is what I managed to do so far using jQuery post.
I've been able to display the timer. In the PHP I've set the target time to 99*60 seconds but I cant set the starting time to 0 as I'll do the difference beteen those to values for the countdown.
Furthermore, as each user is able to quit the page I want to be able to store the time when they left. All I am able to do is store the countdown value, let's say 5845, in the DB when they log off. Though I tried updating the table with each call to the jQuery post, it just makes it worse.
Here is my jQuery:
function countdown() {
var i = (new Date().getTime() / 1000) + (99 * 60);
setTimeout(function () {
$.post(\'countdown.php\',{target:i},function(data){
$('#countdown').html(data);
});
countdown();
},1000);
}
countdown();
Here is the PHP:
if (!empty($resm['Countdown']) || $resm['Countdown'] >= 0) {
$target = (99 * 60);
$countdown = ($target - $current);
$_SESSION['currenttime'] = $countdown;
$hours = floor($countdown / 3600);
$min = floor($countdown / 60);
$r_min = floor(($countdown - ($hours * 3600)) / 60);
$sec = floor($countdown - ($min * 60));
if ($min == 0) {
echo $target.' '.$current.' '.$countdown;
echo '<br/>'.$min.' minutes '.$sec.' seconds left';
} else {
echo 'Time Over';
$sql = "UPDATE bs10000099 SET Upgradedlevel='2',Activated='2',Countdown='5940' WHERE MemberID='$memberid'";
mysql_query($sql);
}
}
I cant figure out how to set the starting time or how to prevent countdown() restart on refresh page.

Answer 1

I'm not sure what kind of security you want, but getting time from Javascript is not really secure since JS gets the time from the computer instead of the server.
With your example, I would be able to play the game, wait until there's 10 minute left, and just roll back time on my desktop and it will reset. Or roll back a year and have 100000 minutes left!
I suggest you use server time.
Here is what I would do:
When the test starts, get the UNIX time + 90 minutes. This will give you the final time.
PHP
if (!isset($_SESSION['end'])) {
$_SESSION['end'] = strtotime("+90 minutes");
}
$remaining = $_SESSION['end'] - time();
if ($remaining > 0) {
echo json_encode(array(
"remaining" => $remaining
));
} else {
// finished! write code here.
}
You can then do a simple $.getJSON() to get the remaining seconds and display it.
Since you kept the "end" time, even if the users leave, the timer will continue.