How to calculate number of Sundays of a particular month and year?

function countSundays($year, $month, $ignore) { $count = 0; $counter = mktime(0, 0, 0, $month, 1, $year); while (date("n", $counter) == $month) { if (in_array(date("w", $counter), $ignore) == false) { $count++; } $counter = strtotime("+1 day", $counter); } return $count; } echo countDays(2013, 1, array(0, 6));