Re: Protected inheritance hierarchies

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 > > I believe classes should be able to access protected properties on their > siblings if the property in question was declared by a shared parent, > but it seems both the engine and reflection (ie. getDeclaringClass) > think that redeclaring a protected property makes it a property of the > child, not the parent. > > This is particularly confusing since the parent class *can* access the > child class' redeclared protected property, only the sibling can't. > > Properties were invariant until the introduction of property hooks, so > the only edge cases I can think of would be in property hooks (But when > the input is correctly typed this shouldn't be a problem either) > > Is there a technical reason for this behavior or would it be possible to > relax this? > > - Jonathan > 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