根据时间间隔检查变量更改（PHP + HTML）

Question

so i am just wondering if i could do this:

a basic site, nothing on it but 4 different photos that have different priority levels which indicate the time-span of actually displaying an image ( lvl1=1min, lvl2=3min, lvl3=10min...and so on) How could i do this with html and php.. I am not sure if answer is really basic but i cant seem to get my head around it. Is html code running parallel to php code or does an infinite while loop in php stop the whole html code in process?

I was thinking of creating an infinite while loop in but i am worried it would eventualy somehow crash the site?

I guess i dont understand how html code runs..

Thanks to anyone who helps.

Answer 1

For you purpose you can use AJAX which is update your code on given time interval. If you want to set something on a timer, you can use JavaScript's setTimeout or setInterval methods:

setTimeout ( expression, timeout );
setInterval ( expression, interval );

Here expression is a normal function and timeout and interval are integers in milliseconds. setTimeout runs the timer once and runs the expression once whereas setInterval will run the expression every time the interval passes.

So in your case it would work something like this:

setInterval(function() {
    //call $.ajax here
}, 5000); //5 seconds

As far as the Ajax goes, see jQuery's ajax() method. If you run an interval, there is nothing stopping you from calling the same ajax() from other places in your code.

Anymore expression need please let me know.