Loop through months, accounting for February

addMonths.php

<?php

/*
based on this SO answer - http://stackoverflow.com/a/40877555/134823
*/

$addMonths = function ($date, $months) {
	$orig_day = $date->format('d');
	$date->modify('+'.$months.' months');
	while ($date->format('d') < $orig_day && $date->format('d') < 5) {
		$date->modify('-1 day');
	}
};

$d = new \DateTime('-4 months');
$dates = [];

for ($i = 1; $i <= 4; $i++) {
	$addMonths($d, 1);
	$start = $d->format('Y-m-01');
	$end = new \DateTime($d->format('Y-m-t'));
	$end->modify('+1 day');
	$dates[] = ['start' => $start, 'end' => $end->format('Y-m-d')];
}

echo "<pre>".print_r($dates, true)."</pre>";

?>