dump(date('Y-m-d', strtotime('2018-10-1 +1 day')));
dump(date('Y-m-d', strtotime('2018-10-1 +1 week')));
dump(date('Y-m-d', strtotime('2018-10-1 +1 month')));
dump(date('Y-m-d', strtotime('2018-10-1 +1 year')));
dump(date('Y-m-d', strtotime('2018-10-1 -1 day')));
dump(date('Y-m-d', strtotime('2018-10-1 -1 week')));
dump(date('Y-m-d', strtotime('2018-10-1 -1 month')));
dump(date('Y-m-d', strtotime('2018-10-1 -1 year')));
同理，把2018-10-1换成变量，就可以做很多事了！
ps 由于每个月份的天数不一样 +/- 1 month 特殊日期会有误差
//获取上一个月日期方法
public function getBeforeMonthDate($currentDate)
{
$currentMonthDay = date('t', strtotime($currentDate));
$currentDay = date('d', strtotime($currentDate));
$yearMonth = date('Y-m', strtotime($currentDate));
$beforeMonth = date('Y-m-d', strtotime("$yearMonth -1 month"));
$beforeMonthDay = date('t', strtotime($beforeMonth));
if ($beforeMonthDay < $currentMonthDay && $beforeMonthDay < $currentDay) {
$beforeDate = date("Y-m-d", strtotime("last day of -1 month", strtotime($currentDate)));
} else {
$beforeDate = date('Y-m-d', strtotime("$currentDate -1 month"));
}
return $beforeDate;
}