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

You can just add 1 to the current month and then see if you crossed the year:

$next_year  = $year;
$next_month = ++$month;

if($next_month == 13) {
  $next_month = 1;    
  $next_year++;
}

Similarly for previous month you can do:

$prev_year  = $year;
$prev_month = --$month;

if($prev_month == 0) {
  $prev_month = 12;
  $prev_year--;
}