Wrong month by DateTime::format('F')

[christian-m-travanto]

Wron output by DateTime Format

The following code:

$monthNum = 2;  // 1 January, 3 also March but that is right
$dateObj = DateTime::createFromFormat('n', $monthNum);
echo $dateObj->format('F');
<?php

Resulted in this output:

March

But I expected this output instead:

February

PHP Version

8.2 also older

Operating System

No response

[heiglandreas]

When creating a DateTime-instance only with a month, the remaining values are taken from the current date. So in essence you are calling new DateTime('2025-02-29') which doesn'T exist. So to cater for that the 29th of february "falls over" to the 1st of march.

You can see that when formatting the date fully like here: https://3v4l.org/PWJX8

[heiglandreas]

So this is expected behaviour. If you want to know the monthname you should do something like this:

$date = DateTimeImmutable::createFromFormat('n.d', $monthNum . '.01');

That will set the date to the first and the problem should no longer arise

[heiglandreas]

Besides that: Depending on the usercase you might want to think about using the intl extension and the IntlDateFormatter as that one can provide localized results.

[christian-m-travanto]

Thanks, yes after I read it it was logical and my mistake was obvious.