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

Question

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');

Answer 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