[php-src] Issue #8278: DateTime::createFromFormat("Y/m") will create bad date

Issue: https://github.com/php/php-src/issues/8278 Comment Author: cmb69 From the [docs](https://www.php.net/manual/en/datetime.createfromformat.php): > If format does not contain the character ! then portions of the generated time which are not > specified in format will be set to the current system time. > > If format contains the character !, then portions of the generated time not provided in format, > as well as values to the left-hand side of the !, will be set to corresponding values from the Unix > epoch. > > The Unix epoch is 1970-01-01 00:00:00 UTC. So you can choose which behavior you want to have. The OP is looking for https://3v4l.org/8pQRO. Changing the default would be a serious and unnecessary BC break.