Simple month padder for calendars etc.

Carbon.php

<?php
use Carbon\Carbon;
use Carbon\CarbonInterval;

/**
 * Pads given month to whole weeks.
 *
 * @param int        $year     Year
 * @param int        $month    Month
 * @param int|string $firstDay First day of week index (0 for sunday) or name.
 *
 * @return DatePeriod[]
 */
function paddedMonth($year, $month, $firstDay = 0) {
    if(is_string($firstDay)) {
        $firstDay = array_search($firstDay, ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday']);
    }

    $current = Carbon::createFromDate($year, $month, 1);
    $current->subDays($current->weekDay - $firstDay);

    $weeks = [];
    do {
        $weeks[] = new DatePeriod(clone $current, CarbonInterval::day(), $current->addWeek());
    } while($current->month == $month);

    return $weeks;
}

DateTime.php

<?php
/**
 * Pads given month to whole weeks.
 *
 * @param int        $year     Year
 * @param int        $month    Month
 * @param int|string $firstDay First day of week index (0 for sunday) or name.
 *
 * @return DatePeriod[]
 */
function paddedMonth($year, $month, $firstDay = 0)
{
    if (is_string($firstDay)) {
        $firstDay = array_search(
            $firstDay, ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday']
        );
    }

    $current = DateTime::createFromFormat('d.m.Y', "1.$month.$year");
    $current->modify('-' . ($current->format('w') - $firstDay) . ' day');

    $weeks = [];
    do {
        $weeks[] = new DatePeriod(clone $current, new DateInterval('P1D'), $current->modify('+1 week'));
    } while ($current->format('m') == $month);

    return $weeks;
}

example.php

<?php
foreach (padMonth(2016, 3) as $week) {
    foreach ($week as $day) {
        echo $day->format('d') . "\t";
    }

    echo PHP_EOL;
}

# 29      01      02      03      04      05      06
# 07      08      09      10      11      12      13
# 14      15      16      17      18      19      20
# 21      22      23      24      25      26      27
# 28      29      30      31      01      02      03