[php-src] Issue #19128: ReflectionProperty::isProtectedSet() not working as expected

Issue: https://github.com/php/php-src/issues/19128 Author: damek24 ### Description The following code: ```php <?php class TestClass { public function __construct( public private(set) int $a, public protected(set) int $b, public readonly int $c, ) { } } class Test2Class extends TestClass { public function setProp(int $x) { $this->c = $x; } } $r = new \ReflectionClass(\TestClass::class); $properties = $r->getProperties(); $x = array_map(fn($prop) => ['private_set' => $prop->isPrivateSet(), 'protected_set' => $prop->isProtectedSet()], $properties); print_r($x); $y = new \Test2Class(1,2,3); $y->setProp(5); ``` Resulted in this output: ``` [ [ "private_set" => true, "protected_set" => false, ], [ "private_set" => false, "protected_set" => true, ], [ "private_set" => false, "protected_set" => true, ], ] Error: Cannot modify readonly property \TestClass::$c. ``` As I did not find this case in the documentation, I am not sure what is the correct behaviour, but I would expect one of two options for the readonly property: 1st option: A readonly property should not be considered as protected(set): ``` [ "private_set" => false, "protected_set" => false, ], ``` for readonly property $c 2nd option: If a readonly property is considered protected(set), then the property should be modifiable in subclasses (but it is not): No error should be thrown during the following method call: $y->setProp(5); // Currently throws: Error: Cannot modify readonly property ### PHP Version ```plain PHP 8.4.10 (cli) (built: Jul 3 2025 12:41:53) (NTS) Copyright (c) The PHP Group Built by Debian Zend Engine v4.4.10, Copyright (c) Zend Technologies with Zend OPcache v8.4.10, Copyright (c), by Zend Technologies ``` ### Operating System _No response_