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First day! = "First day of this month"

In PHP, there is a very strange behavior when using the "first day" to change the date.

'first day' ' of'? Sets the day of the first of the current month. ( http://php.net/manual/de/datetime.formats.relative.php )

 $currentMonthDate = new DateTime("2014-07-30 10:26:00.000000"); echo $currentMonthDate->format('Ym'); $currentMonthDate->modify('first day'); echo $currentMonthDate->format('Ym');

201407/201407 OK

 $currentMonthDate = new DateTime("2014-07-31 10:26:00.000000"); echo $currentMonthDate->format('Ym'); $currentMonthDate->modify('first day'); echo $currentMonthDate->format('Ym');

201407/201408 WHY?

 $currentMonthDate = new DateTime("2014-08-01 10:26:00.000000"); echo $currentMonthDate->format('Ym'); $currentMonthDate->modify('first day'); echo $currentMonthDate->format('Ym');

201408/201408 OK

I found this behavior on our production server running PHP 5.2, so I assumed that this is an ancient error, but it occurs in PHP 5.3 ( http://phptester.net/ ) and 5.5 on our test server.

If I use the "first day of this month" in PHP 5.2, the same behavior occurs. In PHP 5.5, the "first day of this month" works as expected.

Is the "first day" a mistake? And how to get the "first day of this month" in PHP 5.2 without doing weird conversions between string and date ?

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1 answer

This problem seems to be related to the documentation problem.

From Derick in error # 51096: "first day" and "last day" should be "+1 day" and "-1 day".

The documentation should be updated to reflect this behavior, as the "first / last day" section currently says that "from" is optional when it is not.

UPDATE

The documentation is now fixed. So ' of'? is no longer optional.

'first day of' Sets the day of the first of the current month.

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