split date range into months ranges

splitByMonths.php

<?php
function getMonthRanges($start, $end)
{
	$timeStart = strtotime($start);
	$timeEnd   = strtotime($end);
	$out       = [];

	$milestones[] = $timeStart;
	$timeEndMonth = strtotime('first day of next month midnight', $timeStart);
	while ($timeEndMonth < $timeEnd) {
		$milestones[] = $timeEndMonth;
		$timeEndMonth = strtotime('+1 month', $timeEndMonth);
	}
	$milestones[] = $timeEnd;

	$count = count($milestones);
	for ($i = 1; $i < $count; $i++) {
		$out[] = [
			'start' => $milestones[$i - 1],
			'end'   => $milestones[$i] - ($i>=$count-1?0:1)
		];
	}

	return $out;
}

function applyFormat(&$item)
{
	$item = date('Y-m-d H:i:s', $item);
}


$result = getMonthRanges('15-10-2014', '19-03-2015');

array_walk_recursive($result, 'applyFormat');

print_r($result);