如何得到每个月的第二个星期日之间的两个日期

您可以使用与DateTime类一起使用的相对格式，如:

$start_date = new DateTime('2016-08-24');
$end_date = new DateTime('2017-09-24');
$dt = clone $start_date;
$dt->modify('first day of this month')->modify('+2 Sundays');
while ($dt <= $end_date) {
    if ($dt >= $start_date) $result[] = $dt->format('Y-m-d');
    $dt->modify('first day of next month')->modify('+2 Sundays');
}
print_r ($result);

输出为:

Array
(
    [0] => 2016-09-11
    [1] => 2016-10-09
    [2] => 2016-11-13
    [3] => 2016-12-11
    [4] => 2017-01-08
    [5] => 2017-02-12
    [6] => 2017-03-12
    [7] => 2017-04-09
    [8] => 2017-05-14
    [9] => 2017-06-11
    [10] => 2017-07-09
    [11] => 2017-08-13
    [12] => 2017-09-10
)

请使用php类DateTime和DateInterval。在DateInterval手册页上有类似您的问题的代码示例。

试试这个

    $startdate = '2016-08-24';
   $enddate = '2017-09-24';
    getSundays($startdate,$enddate);
    function getSundays($startdate,$enddate) {
        $startweek=date("W",strtotime($startdate));
        $endweek=date("W",strtotime($enddate));
        $year=date("Y",strtotime($startdate));
        for($i=$startweek;$i<=$endweek;$i++) {
            $result=getWeek($i,$year);
            if($result>$startdate&&$result<$enddate) {
                echo date('Y-m-d', strtotime('second sunday of '.date("F",strtotime($startdate)).' '.$year)).'<br/>';
                //echo " Sunday:"."<br>";
            }
        }
    }
    function getWeek($week, $year) {
      $dto = new DateTime();
      $result = $dto->setISODate($year, $week, 0)->format('Y-m-d');
      return $result;
    }