Print out the last day of the month with an interval optionally showing the end date.

gistfile1.php

<?php

$includeEndTime = true;
$interval =  \DateInterval::createFromDateString('last day of next month');
$start = new \DateTime("last day of January 2000");
$end = new \DateTime("last day of December 2001");

if(true === $includeEndTime) {
    $end->add($interval);
}

$datePeriod = new \DatePeriod($start, $interval, $end);
foreach($datePeriod as $date) {
    var_dump($date);
}