PHP倒计时计时器操作

Hi all apologies if this is an easy solution, I am creating an test application and require that a timer is started when the user clicks on the test. I am however completely confused how to implement a counter for the application - and how to trigger an action when the timer has reached 0.

I have found implementations of JS timers/countdowns:

PHP Timer wait 30 seconds then run a command

PHP when countdown runs out

and a php timer:

Start and stop a timer PHP

I was hoping that someone could help me with an example of a PHP timer that triggers an action when it has reached 0 for example - redirecting to another page.

Many thanks in advance - please have patience, I am a total beginner

Using JQuery:

function runTimer(seconds, yourUrl) {
  setTimeout(function() {
    $.get(yourUrl);
  }, seconds * 1000;
}

run it:

runTimer(5, 'http://example.com/action.php');

But it won't be possible to redirect to other page using ajax request.

For redirecting use:

function runTimerRedirect(seconds, yourUrl) {
  setTimeout(function() {
    window.location = yourUrl
  }, seconds * 1000;
}