On Sat, Aug 2, 2025, at 22:17, Rob Landers <rob@bottled.codes> wrote:
> On Sat, Aug 2, 2025, at 19:04, Alexandru Pătrănescu wrote: > > > > On Sat, Aug 2, 2025, 17:10 Rob Landers <rob@bottled.codes> wrote: > > > > > On Sat, Aug 2, 2025, at 16:04, Alexandru Pătrănescu wrote: > > > > On Sat, Aug 2, 2025 at 12:10 PM Rob Landers <rob@bottled.codes> wrote: > > > On Tue, Jul 29, 2025, at 20:11, Jonathan Vollebregt wrote: > > I came across this edge case today: > > https://3v4l.org/R3Q8D > > Both psalm and phpstan think this code is A-OK (Once you add the > requisite type hints) but it causes fatal errors way back to PHP 5.0.0 > > ...<snip>... > > > It's not an edge case, in C2, you redefine a protected variable with the > same name and shadowed the original $v. That $v is different than C's $v. > It's easiest to see this with static access: > https://3v4l.org/0SRWb#v8.4.10 > > However, I don't know of any way to unshadow a property from $this to > access the ancestor's value (other than using private access), but it > exists and takes up memory; just accessing it is the hard part. > > — Rob > > > > Hi Rob, > > I'm pretty sure that there is no shadowing happening in the example. > When the child instance is created, there is just one slot for the > property, as the child one replaces the parent one. > So basically the child property overrides the parent property rather than > shadowing it. > > True shadowing (two slots) only occurs when the parent property is > declared private. > > It's just that when redefining, it stores the declaring class, and so > there is this sibling class access issue. > > I'm wondering now if the access shouldn't be relaxed, in case we have the > parent class that initially defined the property. > > Of course, we should focus on non-static properties, as static ones are > different things, and there is some shadowing there. > > -- > Alex > > > Hi Alex, > > I’m not sure what you mean? https://3v4l.org/WKILh#v8.4.10 > > There is clearly shadowing going on. > > > > Hi Rob, > > As I said, let's leave aside the static case, as the question from > Jonathan was not about that. > > Given the class P that defines a protected property with value 1, > and a class C that extends P and re-defines the protected property with > the value 2, > please show me an example where you could get from an instance of class C > the value 1 of the parent class property that you think it's shadowed. > Bonus point, if you manage that, you could also set it to something else, > and so have a hidden storage for any object of class C that is not really > visible normally. > > As far as I know, there is no way to achieve that, and the reason is > because at runtime the objects have a single slot for the protected > property; the child class property overrides the parent class property when > redeclared, and does not shadow it. > But please prove me wrong. > > > Thanks, > Alex > > > I mentioned in my first reply, there is no way to get an instance-level > property unshadowed. It is there though (according to inheritance.c, if I’m > reading it right, it is still accessible, just not from user-land). > > In any case, there are lots of interesting footguns with properties and > inheritance: Problem with abstract nested object · Issue #47 · Crell/Serde > <https://github.com/Crell/Serde/issues/47#issuecomment-1890966829>. > > Could it be considered a bug that my first example produces a fatal > error instead of trying to access the shadowed parent property that it > has access to and is typed to use? > > > Other languages (such as C#, Java, etc: > https://www.programiz.com/online-compiler/0ud6UO24mHOTU) don’t allow you > to access protected properties/methods on sibling classes. This is because > "protected" is usually used in the context of inheritance; access is > usually restricted to "myself" or "children" and a sibling is neither of > those. If there is a bug, the bug is that you can access a sibling’s > protected properties, at all. > > — Rob > > If there is a bug, the bug is that you can access a sibling’s protected properties, at all. In 2006 the absence of this feature was fixed as a bug and meged in PHP 5.2: https://bugs.php.net/bug.php?id=37632 In 2020 Nikita Popov agreed that this is expected: https://x.com/nikita_ppv/status/1261633126687805440 So one way is to explicitly mention this feature in the Visibility docs <https://www.php.net/manual/en/language.oop5.visibility.php> and fix the redeclaration issue to make things consistent. The other way is to deprecate sibling relations. -- Valentin
