Static class constants

[Digitalone1]

Description

Please, consider this script: https://3v4l.org/bnclg#v8.4.3

As you can see, accessing a static property with object operator (->) is deprecated. If we read it, it's undefined. And if we try to write on it, a dynamic property is created (which is also deprecated).

Everything is OK if we read the same property with scope operator (::), but we can also modify it if we assign it another value. This means the static class properties are variable and we have no way to make them constant.

Indeed if we do:

class Foo
{
    public static const string MY_STATIC = "foo";
}

We get a Fatal error: Cannot use the static modifier on a class constant.

I wonder if this is intended for some reason or it's a missing feature. Maybe I want some properties to be available for the user without initializing the class instance, but the user can still modify them even if it would be better if they are not allowed to.

[cmb69]

Class constants are implicitly static, i.e. available on the class. See https://3v4l.org/OnMvp.

[Digitalone1]

Class constants are implicitly static, i.e. available on the class. See https://3v4l.org/OnMvp.

Wow, this is not clearly stated in the documentation. Good to know. Thanks.

[cmb69]

From https://www.php.net/manual/en/language.oop5.constants.php:

Note that class constants are allocated once per class, and not for each class instance.

In my opinion, good enough (with the rest of that page).

[Digitalone1]

In my opinion, good enough (with the rest of that page).

I don't think so. The main feature of static class properties is to make them accessible without needing an instantiation of the class, as stated in the static keyword documentation.

This is not stated in the class constants documentation and saying it's allocated once per class maybe is enough for experienced users, but not everyone.

Besides, I have to say that making class constants as static without the static keyword is quite misleading. But you had your reasons to do so. It's okay anyway.

[iluuu1994]

I don't think so. The main feature of static class properties is to make them accessible without needing an instantiation of the class, as stated in the static keyword documentation.

It's stated in the quote Christoph linked. It says it's allocated per class, not instance. Hence, you don't need an instance.

[cmb69]

I have to admit, though, that this still is a bit confusing, since all methods are also "allocated" on the class. ¯\(ツ)/¯

[iluuu1994]

But methods also aren't storage, so not exactly comparable.