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

Issue: https://github.com/php/php-src/issues/8278 Comment Author: bwoebi I'm really wondering whether it makes sense to default to the current day instead of the first of a month when parsing a date containing month and/or year information, but no day. Similarly defaulting to the current month when the date contains a year, but no month. Could be just January by default. @derickr Is there any reason why it _has_ to work this way? To me it just seems like a constant source of confusion.