How to get the previous and next month?

Question

$year  = 2010;
$month = 10;

How do I get the previous month 2010-09 and next month 2010-11?

Answer 1

$prevMonth = $month - 1;
$nextMonth = $month + 1;
$prevYear = $year;
$nextYear = $year;

if ($prevMonth < 1) {
    $prevMonth = 1;
    $prevYear -= 1;
}

if ($nextMonth > 12) {
    $nextMonth = 1;
    $nextYear += 1
}

or

// PHP > 5.2.0
$date = new DateTime();
$date->setDate($year, $month, 1);
$prevDate = $date->modify('-1 month');
$nextDate = $date->modify('+1 month');
// some $prevDate->format() and $nextDate->format()