ReflectionProperty::isProtectedSet() not working as expected #19128
Description
Description
The following code:
<?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
PHP 8.4.10 (cli) (built: Jul 3 2025 12:41:53) (NTS)
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