<?php
$start = new DateTime('2018-12-31 00:00:00');
$end = new DateTime('2021-12-31 00:00:00');
$interval = new DateInterval('P1M');
$recurrences = 5;
// 通过构造函数显式设置重复次数
$period = new DatePeriod($start, $interval, $recurrences, DatePeriod::EXCLUDE_START_DATE);
echo $period->recurrences, "\n";
$period = new DatePeriod($start, $interval, $recurrences);
echo $period->recurrences, "\n";
$period = new DatePeriod($start, $interval, $recurrences, DatePeriod::INCLUDE_END_DATE);
echo $period->recurrences, "\n";
// 构造函数中没有设置重复次数
$period = new DatePeriod($start, $interval, $end);
echo $period->recurrences, "\n";
$period = new DatePeriod($start, $interval, $end, DatePeriod::EXCLUDE_START_DATE);
echo $period->recurrences, "\n";
?>