Slice a given periods into multiples periods cut on months

cut_period_between_months.php

<?php

/**
 * Slice a given periods into multiples periods cut on months
 *
 * Example: 15/01 - 15/02 = 15/01 - 31/01 : 01/02 - 15/02
 *
 * @param DateTime $start
 * @param DateTime $end
 * @yield array whith keys `start` & `end` containing `DateTime` formated
 */
function cutPeriodBetweenMonths(DateTime $start, DateTime $end)
{
    while ($start < $end) {
        // get the last month of the `$start` date (`Y-m-t` return the last day)
        $endMonth = DateTime::createFromFormat('Y-m-d', $start->format('Y-m-t'));

        if ($endMonth < $end) {
            // get the first month of previous week
            $startMonth = clone $endMonth;
            $startMonth->add(new DateInterval('P1D'));

            yield [
                'start' => $start->format('Y-m-d'),
                'end'   => $endMonth->format('Y-m-d'),
            ];

            $start = $startMonth;
        } else {
            yield [
                'start' => $start->format('Y-m-d'),
                'end'   => $end->format('Y-m-d'),
            ];
            break;
        }
    }
}


// Usage example
$start   = DateTime::createFromFormat('Y-m-d', '2017-01-15');
$end     = DateTime::createFromFormat('Y-m-d', '2017-05-15');
$periods = cutPeriodBetweenMonths($start, $end);
var_export(iterator_to_array($periods));
//[
//    0 => [
//        'start' => '2017-01-15',
//        'end'   => '2017-01-31',
//    ],
//    1 => [
//        'start' => '2017-02-01',
//        'end'   => '2017-02-28',
//    ],
//    2 => [
//        'start' => '2017-03-01',
//        'end'   => '2017-03-31',
//    ],
//    3 => [
//        'start' => '2017-04-01',
//        'end'   => '2017-04-30',
//    ],
//    4 => [
//        'start' => '2017-05-01',
//        'end'   => '2017-05-15',
//    ],
//]