Count number of months by day in php - php

Question

I want to get month between two dates. I've googled a lot but still don't have the answer.
$date1 = new \DateTime("2021-07-20");
$date2 = new \DateTime("2021-08-15");
$interval = $date2->diff($date1);
dd($interval->m); // 0 months.
Above, counting $date1 and $date2 is less than 30 days so it returns 0 months which is correct. But now I want to get the result 2. It's July and August. Is there any way to get that?
Thanks

Answer 1

I tried a few approaches to tackle this.
The easiest method I've found that works for all use cases involves using regular math rather than date functions. The date diff methods I've tried all gave incorrect answers at some point because of the differing number of days in a month.
function getCoveredMonths(DateTime $date1, DateTime $date2): int {
$earlierDate = min($date1, $date2);
$laterDate = max($date1, $date2);
$earlierMonthValue = $earlierDate->format("Y") * 12 + $earlierDate->format("n");
$laterMonthValue = $laterDate->format("Y") * 12 + $laterDate->format("n");
return $laterMonthValue - $earlierMonthValue + 1;
}
// Your example
$date1 = new DateTime("2021-07-20");
$date2 = new DateTime("2021-08-15");
var_dump(getCoveredMonths($date1, $date2));
// 2: July + August
// Same month
$date3 = new DateTime("2021-07-15");
$date4 = new DateTime("2021-07-20");
var_dump(getCoveredMonths($date3, $date4));
// 1: July
// Day overflow test (01-30 + 1 month = 02-30 which overflows to 03-02)
$date5 = new DateTime("2021-01-30");
$date6 = new DateTime("2021-03-01");
var_dump(getCoveredMonths($date5, $date6));
// 3: January + February + March
// Year pass test
$date7 = new DateTime("2021-12-20");
$date8 = new DateTime("2022-02-15");
var_dump(getCoveredMonths($date7, $date8));
// 3: December + January + February
// Wrong order ($date2 is before $date1)
$date9 = new DateTime("2021-10-20");
$date10 = new DateTime("2021-08-15");
var_dump(getCoveredMonths($date9, $date10));
// 3: August + September + October

Answer 2

<?php
$origin = new \DateTime('2020-08-01');
$target = new \DateTime('2021-12-01');
$interval = $origin->diff($target);
echo (($interval->format('%y') * 12) + $interval->format('%m'));
// output is 16 months
?>

Answer 3

If you want to calculate with the full months, you have to calculate from the 1st of the start month to the 1st after the end of the month.
$date1 = new \DateTime("2021-07-20");
$date2 = new \DateTime("2021-08-15");
//
$date1->modify('first day of this Month'); //2021-07-01
$date2->modify('first day of next Month'); //2021-09-01
$interval = $date1->diff($date2);
$countMonth = $interval->m; //2