Strange behavior of `ReflectionClass::getProperty` with trait and inheritance

[HypeMC]

Description

The following code: https://3v4l.org/Zbnqa

<?php

class ParentClass
{
    protected readonly int $value;
}

trait Foo
{
    protected readonly int $value;
}

class ChildClassWithoutTrait extends ParentClass
{
    protected readonly int $value;
}

$reflector = new ReflectionClass(ChildClassWithoutTrait::class);
$instance = $reflector->newInstanceWithoutConstructor();

var_dump(
    $reflector->hasProperty('value'),
    $prop = $reflector->getProperty('value')
);

$prop->setValue($instance, 20);

var_dump($instance);

echo '--------------------------------------------------------------------------------------------------------', PHP_EOL;

class ClassWithTraitAndNoParent
{
    use Foo;
}

$reflector = new ReflectionClass(ClassWithTraitAndNoParent::class);
$instance = $reflector->newInstanceWithoutConstructor();

var_dump(
    $reflector->hasProperty('value'),
    $prop = $reflector->getProperty('value')
);

$prop->setValue($instance, 20);

var_dump($instance);

echo '--------------------------------------------------------------------------------------------------------', PHP_EOL;

class ChildClassWithTrait extends ParentClass
{
    use Foo;
}

$reflector = new ReflectionClass(ChildClassWithTrait::class);
$instance = $reflector->newInstanceWithoutConstructor();

var_dump(
    $reflector->hasProperty('value'),
    $prop = $reflector->getProperty('value')
);

$prop->setValue($instance, 20);

var_dump($instance);

Resulted in this output:

bool(true)
object(ReflectionProperty)#3 (2) {
  ["name"]=>
  string(5) "value"
  ["class"]=>
  string(22) "ChildClassWithoutTrait"
}
object(ChildClassWithoutTrait)#2 (1) {
  ["value":protected]=>
  int(20)
}
--------------------------------------------------------------------------------------------------------
bool(true)
object(ReflectionProperty)#2 (2) {
  ["name"]=>
  string(5) "value"
  ["class"]=>
  string(25) "ClassWithTraitAndNoParent"
}
object(ClassWithTraitAndNoParent)#1 (1) {
  ["value":protected]=>
  int(20)
}
--------------------------------------------------------------------------------------------------------
bool(true)
object(ReflectionProperty)#1 (2) {
  ["name"]=>
  string(5) "value"
  ["class"]=>
  string(11) "ParentClass"
}

Fatal error: Uncaught Error: Cannot initialize readonly property ParentClass::$value from scope ChildClassWithTrait in /in/Zbnqa:64
Stack trace:
#0 /in/Zbnqa(64): ReflectionProperty->setValue(Object(ChildClassWithTrait), 20)
#1 {main}
  thrown in /in/Zbnqa on line 64

Process exited with code 255.

But I expected this output instead:

bool(true)
object(ReflectionProperty)#3 (2) {
  ["name"]=>
  string(5) "value"
  ["class"]=>
  string(22) "ChildClassWithoutTrait"
}
object(ChildClassWithoutTrait)#2 (1) {
  ["value":protected]=>
  int(20)
}
--------------------------------------------------------------------------------------------------------
bool(true)
object(ReflectionProperty)#2 (2) {
  ["name"]=>
  string(5) "value"
  ["class"]=>
  string(25) "ClassWithTraitAndNoParent"
}
object(ClassWithTraitAndNoParent)#1 (1) {
  ["value":protected]=>
  int(20)
}
--------------------------------------------------------------------------------------------------------
bool(true)
object(ReflectionProperty)#1 (2) {
  ["name"]=>
  string(5) "value"
  ["class"]=>
  string(11) "ChildClassWithTrait"
}
object(ChildClassWithTrait)#n (1) {
  ["value":protected]=>
  int(20)
}

It seems that a combination of traits and inheritance somehow breaks the getProperty() method. Even though the hasProperty() method returns true for ChildClassWithTrait, the getProperty() method returns a ReflectionProperty for ParentClass.

PHP Version

all

Operating System

No response

[iluuu1994]

Simplified example:

class ParentClass {
    protected readonly int $value;
}

trait Foo {
    protected readonly int $value;
}

class ChildClassWithTrait extends ParentClass {
    use Foo;

    public function __construct() {
        $this->value = 20;
    }
}

new ChildClassWithTrait();

Given traits are described as "copy & paste" in the documentation, it seems to me that this should work.

[djmarland]

We have also run into this issue, particularly when trying to set Attributes: https://3v4l.org/rZILt

It seems properties from Traits are at the end of the properties list, so will not overwrite earlier properties from the parents.
This means that the attribute values come from the parent instead of the trait used by the child.