[php-src] Issue #8152: Cannot hydrate a DateTime instance created without the constructor

Issue: https://github.com/php/php-src/issues/8152 Author: nicolas-grekas ### Description This report applies to DateTime, DateTimeImmutable, DateTimeZone, DateInterval and DatePeriod. Before PHP 8.2, there used to be a way to create a DateTime object from an uninitialized prototype: ```php $date = (new \ReflectionClass('DateTime'))->newInstanceWithoutConstructor(); $date->date = '1970-01-01 00:00:00.000000'; $date->timezone_type Warning: Undefined property: DateTime::$date in /in/EUrC5 on line 4 NULL string(26) "2022-02-24 22:26:25.005040"= 1; $date->timezone = '+00:00'; $date->__wakeup(); ``` These 3 properties do not exist on DateTime, but they're still returned by serialize($date), that's how I figured out how to hydrate the previous object. And it works perfectly. But since PHP 8.2, a deprecation is triggered because dynamic properties are not allowed. Since means that since 8.2, there is no way to hydrate a DateTime instance that is created without the constructor. This is an issue in symfony/var-exporter for example, which is a library that provides a way to serialize objects to native PHP code (instead of the serialization format). I cannot figure out a way to make this lib support PHP 8.2 while not triggering a warning. Not that the engine allows itself to create those dynamic properties even on PH P8.2. Here is some code to highlight this: ```php $d = new DateTime(); var_dump($d->date); $e = unserialize(serialize($d)); var_dump($e->date); ``` This [outputs](https://3v4l.org/EUrC5/rfc#vgit.master): ``` Warning: Undefined property: DateTime::$date in /in/EUrC5 on line 4 NULL string(26) "2022-02-24 22:26:25.005040" ``` A simple fix would be to add #[AllowDynamicProperties] to those classes. Another fix would be to actually declare the corresponding properties as protected. WDYT?