Exponential backoff

exponential_backoff.php

$stopAt = 15; // 4h 33m 4s
$now = new DateTime;
?><table><?php
foreach (range(1, 15) as $i) {
?><tr><td><?php
        echo $i
?><td><?php
        $after = clone $now;
        $tries = min($i, $stopAt);
        $seconds = (int) ceil( (pow(2, $tries) - 1) / 2 );
        $interval = new DateInterval('PT' . $seconds . 'S');
        $after->add($interval);
	echo $after->format($format = 'Y-m-d H:i:s');
?><td><?php
	$d = new DateTime('@' . $seconds);
	echo $d->format('H:i:s');
?><td><?php
	echo $seconds;
}