[php-src] Issue #8204: Nullsafe Operator doesn't work with uninitialized properties

Issue: https://github.com/php/php-src/issues/8204 Author: iw-rylee ### Description The following code: ```php <?php class SomeClass { public DateTime $date_val; } $some = new SomeClass; // Test 1 echo $some->date_val?->format("Y-m-d") ?? "default"; // Test 2 echo $some?->date_val?->format("Y-m-d") ?? "default"; // Test 3 echo ($some->date_val ?? null)?->format("Y-m-d") ?? "default"; // Test 4 echo ($some?->date_val ?? null)?->format("Y-m-d") ?? "default"; ``` Resulted in this output: ``` // Test 1 - throws Fatal Error // Test 2 - throws Fatal Error // Test 3 - outputs "default" as expected // Test 4 - outputs "default" as expected ``` But I expected this output instead: ``` All tests to output "default" ``` The alternative approach is: ```php class SomeClass { public ?DateTime $date_val = null; } ``` However, doing this "marks" SomeClass::$date_val as "possibly being null". The expected use case for the original class: >A "valid" SomeClass should always have >Ê&¡XÒŸWFèËFh$date typed as DateTime instead of >being typed as null OR DateTime We can potentially: * set $date_val to be protected * override the magic __get method to return $this->{$name} ?? null; This works **outside** the class, but not within it: ```php class SomeClass { protected DateTime $date_val; public function __get(string $name): mixed { return $this->{$name} ?? null; } public function toArray(){ return [ "date_val" => $this->date_val?->format("Y-m-d") ?? "default", ]; } } $some = new SomeClass; // Test 1 - this works and outputs "default" echo $some->date_val?->format("Y-m-d") ?? "default"; // Test 2 - this throws a Fatal Error var_dump($some->toArray()); ``` The magic method __isset() is not called in any of the above cases where a Fatal Exception is thrown. ### PHP Version PHP 8.0.2 ### Operating System Windows 10