[php-src] Issue #10379: Exception::$message can't be extends with string type

Issue: https://github.com/php/php-src/issues/10379 Author: julien-boudry ### Description ### Documentation book The PHP book describes Exception class as follows: https://www.php.net/manual/en/class.exception.php ```php class Exception implements [Throwable](https://www.php.net/manual/en/class.throwable.php) { /* Properties */ protected string $message= ""; [...] } ``` ### The extending it: https://3v4l.org/QtEA0#v8.2.1 ```php <?php class AException extends \Exception { protected $message = 'New Default Message'; } class BException extends \Exception { protected string $message = 'New Default Message'; } ``` Resulted in this output: ``` Fatal error: Type of BException::$message must not be defined (as in class Exception) ``` But I expected this output instead: _No error. Or an error for class A, not class B._ ### PHP Version PHP 8.2.1 ### Operating System *