php coundown auto update issue - php

Question

<?php
//index.php
$current_date = date('Y-m-d H:i:s');
$current_min_sec = date('i:s');
$current_min = date('i');
$array_min= array(0,3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57);
if((int)$current_min >= 57){
$next_slot_time = 0;
}else{
$min = (int)$current_min;
$newNumbers = array_filter(
$array_min,
function ($value) use($min) {
return ($value > $min);
}
);
$next_slot_time = reset($newNumbers);
}
?>
<div id='countdown'></div>
<script type="text/javascript">
const updateWind = () => {
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var valr5 = this.responseText;
document.getElementById("countdown").innerHTML = valr5;
if (valr5 == '00:00'){
window.location = "index.php";
}
}
};
xmlhttp.open("POST", "response.php", true);
xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xmlhttp.send("next_slot="+<?php echo $next_slot_time?>);
};
updateWind();
window.setInterval(updateWind, 1000);
</script>
<?php
//response.php
$time = new DateTime();
$start_timer_time = $time->format('Y-m-d H:i:s');
$end_minute = $_POST['next_slot'];
if($end_minute == 0){
$timeHr = $time->format("H") + 1;
}else{
$timeHr = $time->format("H");
}
$time->setTime($timeHr,$end_minute,00);
$end_timer_time = $time->format('Y-m-d H:i:s');
$from_time = $start_timer_time;
$to_time = $end_timer_time;
$timefirst = strtotime($from_time);
$timesecond = strtotime($to_time);
$diffinsec=$timesecond-$timefirst;
if(gmdate("i:s",$diffinsec) == '00:30'){
echo 'RUN SCRIPT HERE';
}else if(gmdate("i:s",$diffinsec) == '00:00'){
echo gmdate("i:s",$diffinsec);
}else{
echo gmdate("i:s",$diffinsec);
}
?>
I have a script which shows a countdown with a button and table to the users. it has following things
1] Run countdown every 3 min (exactly 20 times in one hour) 2] Show countdown timing same to all users 3] Never reset countdown on user browser refresh 4] On 00.30 button lock through js and internally another php script runs which does some calculation and updates 1 entry to the table 5] On 00.00 when time over page gets refreshed, the countdown starts again and the below table is shown with newly added entry.
This script is working fine when it is open in the browser but not working when no user is accessing this page. I want to run this countdown offline also. I am figuring out two solutions
1] Make one more script, So it will work when index.php is not open by anyone (but don't know how to track when it should run and when its should not run) 2] Make a single script like (cron) job but in that case how do I display countdown to users
I am not aware of possible vulnerabilities. Kindly share your thoughts. Thanks a lot in advance

Answer 1

Yes. It is only achieve by cron job.. Thanks guys for the support