PHP服务器端倒计时

Question

Is there any way I can use PHP to make a countdown timer on the SERVER side?

Like this:

• The countdown timer should be equal to anyone entering the website
• Once the timer hits zero, a code should execute. But only once.

Imagine a jackpot website, once the timer hits zero some queries needs to execute. But if we have 50 people on the site, then 50 queries would execute. So it needs to be server-side. How can I solve that?

Using cronjobs for every second? A web-page open on the VPS that handles the timer by itself on a "secret" link? Some sort of live-php script?

Answer 1

PHP countdown can be coded like this:

//You must call the function session_start() before
//you attempt to work with sessions in PHP!
session_start();

//Check to see if our countdown session
//variable has been initialized.
if(!isset($_SESSION['countdown'])){
    //Set the countdown to 120 seconds.
    $_SESSION['countdown'] = 120;
    //Store the timestamp of when the countdown began.
    $_SESSION['time_started'] = time();
}

//Get the current timestamp.
$now = time();

//Calculate how many seconds have passed since
//the countdown began.
$timeSince = $now - $_SESSION['time_started'];

//How many seconds are remaining?
$remainingSeconds = abs($_SESSION['countdown'] - $timeSince);

//Print out the countdown.
echo "There are $remainingSeconds seconds remaining.";

//Check if the countdown has finished.
if($remainingSeconds < 1){
   //Finished! Do something.
}

Beacuse of PHP nature, this 'timer check' will occur only on page load. If you want to trigger some code execution precisely when counter hits 0 you should use JavaScript for detecting coundtdown pass and trigger with AJAX some PHP code. I know this is not complete solution but it's at least part of it :)