How to create a scheduler application in php

PHP Snippet 1:

// init priorities array in seconds
$schedules = [
    'high'  => 1,
    'medium'=> 5,
    'low'   => 30
];

while($now ??= time()) {
    foreach($schedules as $priority => $seconds)  {
        if($now >= $next[$priority] ??= $now) {
            $next[$priority] += $seconds;
            
            // --> execute your script here for every priority
            // in my case I call high.php, medium.php and low.php with 
            // with execInBackground() by TheUO available here : 
            // https://stackoverflow.com/a/12117258/2282880;
            
            // something like execInBackground("scripts/", "$priority.php");
        }
    }
    time_sleep_until(++$now);
}