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Date: Sun, 03 Aug 2025 10:10:13 +0100
To: internals@lists.php.net
Subject: Re: [PHP-DEV] Protected inheritance hierarchies
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

On 2 August 2025 21:59:20 BST, Rob Landers <rob@bottled=2Ecodes> wrote:
>If this were the case, then creating a base class with default values wou=
ldn=E2=80=99t be possible=2E The memory exists and is set aside for that=2E

Sure it would: the default value is just an assignment that happens at a p=
articular point of the object's lifecycle=2E For a child class which overri=
des the default of a parent (on a public or protected property), only the c=
hild class's assignment will ever be visible=2E So it would be perfectly va=
lid for the class entry for the child class to only store that one assignme=
nt=2E I don't know if that actually happens; maybe the cost of de-duplicati=
ng is not seen as worthwhile, and the assignments are just run in sequence =
every time=2E

Regardless, the philosophical question in this thread seems to be whether =
re-declaring a protected property should change the "ownership" of that pro=
perty=2E I think it's natural that a protected property *only* declared in =
a sibling class can't be accessed, so some ownership needs to be tracked=2E

What seems surprising is that the ownership changes if the same property i=
s re-declared, especially since the new declaration has to match the origin=
al (e=2Eg=2E you can't change the type), and every possible access tells th=
e user the two declarations have been completely merged=2E=20

Intuitively, an identical declaration with no change other than a default =
value looks like it would be the same as overwriting the default in a const=
ructor, but that is not the case=2E (https://3v4l=2Eorg/5iIak vs https://3v=
4l=2Eorg/rL8pX)

I'm inclined to agree that this is a bug, regardless of whether it's diffi=
cult to fix in the implementation=2E


Rowan Tommins
[IMSoP]