How can i parse a date to same day of previous month?

问题

How can i parse a date to same day of previous month in PHP?

Example:

   input                 Output

2018-07-25     ->       2018-06-25
2018-07-31     ->       2018-06-30 (because there is no 31)

My code

$d = "2018-07-25";
$xd = date_parse_from_format("y-m-d", $d last month);
$output_d = date_create($xd)->format('Y-m-d');

回答1:

<?php
$date = new DateTimeImmutable("2018-07-31");
$previous = $date->sub(new DateInterval('P1M'));
$lastMonth= $date->modify('last day of previous month');
if ($previous > $lastMonth) {
    $previous = $lastMonth;
}
echo $previous ->format('Y-m-d');

This code subtracts one month from the current date. If it is greater than the last day of the previous month we use the last day of the previous month instead.

Demo

回答2:

Going back to one month is like subtracting one month from the existing date so with the help of strtotime and date we can solve this. like,

$a = "2018-07-25"; $b = date("Y-m-d",strtotime($a."-1 month")); $b is 2018-06-25

Hope this helps.

来源：https://stackoverflow.com/questions/51285654/how-can-i-parse-a-date-to-same-day-of-previous-month