How to make countdown timer like in browser games? [closed] - php

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I would like to know how to make countdown timer in PHP. In browser games, for example; when you build up a building or do start a research, a countdown starts for that building etc.. and when you shut down computer or website and open it back from another computer or somewhere else you see that the countdown is still working. Could you briefly explain how it works or what should I search on google to have some idea about it?
Thank you!

Answer 1

You store the time on the server, it could be either the time something started (and you need to know the duration) or the time it ends.
On the client-side, you read this value and make a timer that will tick inside the browser, based on the time you fetched from the server.
Here's a super-simple example that will use browser's localStorage to store the time value. It will show the time passed since you first opened the example: http://jsfiddle.net/ceyw1v5a/
Try refreshing the link to see how the timer value is persistent. I wanted to do it here as a snippet, but it's doesn't allow localStorage for security reasons.
Anyway, because the client-side timer can be easily tampered with, you should never, ever rely on it! That means, say you have a game, and when a certain time expires, you get a gold coin, you should always check for the time expiry on the server because malicious users can easily set the timer to zero and make the server call, but it's up to that server to figure out whether the time had really expired or there's a cheat attempt.
UPDATE
when you build up a building or do start a research, a countdown starts for that building etc..
In that case, the process would go something like this:
user clicks the build button
a server call is made to check if you're allowed to build it (check resources, etc...) and if so, it stores the timestamp when the construction of that particular building has started
based on the construction duration, the timer appears on the client side (the browser), counting down
if the user reconnects, the "currently building" values for all the buildings are read from the server side storage, and the client side timer is relaunched based on the remaining duration
when the timer expires on the client side, a server call is made (as described above), and if the timer on the server side has expired as well (meaning the building is complete), you remove the timer on the client side and show the completed building
if the user leaves before the building is complete and reconnects after it's complete, you simply show the completed building on the client side, no timers needed
About the actual process of getting the data from the server will vary, depending on your app structure. For example, you can make AJAX call(s) to fetch the server data when the game runs, etc.

Answer 2

Use php to get the current time and calculate the end time of the event.
<?php
$event_action_time = "3600"; // 1 hour in seconds
$time = time(); // current time
$endtime = $time + $event_action_time; // future date for event to end
// Store endtime in DB
?>
Now that you have the end time you can query the db for any events that have not ended based on the current time. If there are results you can then assign the end time result to a variable in php and pass it to preferably a jquery countdown.