[PHP-DEV] [RFC] [Discussion] `#[\Override]` for class constants

Mailing Lists php.internals
1

Hi internals,

I’d like to start the discussion for a new RFC about adding support for #[\Override] for class constants.

I’d also like to draw specific attention to the open question, which I am soliciting feedback on: how should #[\Override] work for enum cases? See the RFC page for details.

Thanks,
-Daniel

2

On 31 March 2026 00:36:42 BST, Daniel Scherzer <daniel.e.scherzer@gmail.com> wrote:

Hi internals,

I'd like to start the discussion for a new RFC about adding support for
`#[\Override]` for class constants.

* RFC: PHP: rfc:override_constants
* Implementation: [RFC] Allow `#[\Override]` on class constants by DanielEScherzer · Pull Request #20478 · php/php-src · GitHub

I will probably abstain on this, because I've never fully understood the rationale for this attribute, but one point that might be worth spelling out is that by nature constants are static, which makes it slightly harder to accidentally reference an overridden definition. "Foo::BAR" and "self::BAR" are both guaranteed to reference the expected definition; only less common forms like "static::BAR" and "$this::BAR" will look up on a sub-class.

Rowan Tommins
[IMSoP]

3

On Mon, 30 Mar 2026, Daniel Scherzer wrote:

I'd like to start the discussion for a new RFC about adding support for
`#[\Override]` for class constants.

* RFC: PHP: rfc:override_constants
* Implementation: [RFC] Allow `#[\Override]` on class constants by DanielEScherzer · Pull Request #20478 · php/php-src · GitHub

I'd also like to draw specific attention to the open question, which I am
soliciting feedback on: how should `#[\Override]` work for enum cases? See
the RFC page for details.

I think I'm on the " Always reject using #[\Override] on an enum case,
saying that the attribute does not target enum cases" side here, as
mixing class constants with enum cases sounds like a mismatch to me.

cheers,
Derick

4

On Tuesday, 31 March 2026 at 00:45, Daniel Scherzer <daniel.e.scherzer@gmail.com> wrote:

Hi internals,

I'd like to start the discussion for a new RFC about adding support for `#[\Override]` for class constants.

* RFC: PHP: rfc:override_constants
* Implementation: [RFC] Allow `#[\Override]` on class constants by DanielEScherzer · Pull Request #20478 · php/php-src · GitHub

I'd also like to draw specific attention to the open question, which I am soliciting feedback on: how should `#[\Override]` work for enum cases? See the RFC page for details.

It's impossible to override an enum case. Enums are final and cannot be extended. So just error if someone tries to use `#[\Override]` on an enum case as it is non-sensical.

Best regards,
Gina P. Banyard

5

Hi

Am 2026-03-31 01:36, schrieb Daniel Scherzer:

I'd also like to draw specific attention to the open question, which I am
soliciting feedback on: how should `#[\Override]` work for enum cases? See
the RFC page for details.

We've been pretty clear so far the “enum cases are just constants”, e.g. in the RFC for `#[\Deprecated]` (PHP: rfc:deprecated_attribute):

Enum cases are internally implemented as class constants. Adding the #[\Deprecated] attribute to an enum case will behave as expected.

Given that:

     interface NamedX {
         public const string Name = 'foo';
     }

     enum Foo implements NamedX {
         case Name;
     }

is a thing already and fails with:

     Type of Foo::Name must be compatible with Named::Name of type string

as expected and

     interface NamedX {
         public const Name = 'foo';
     }

     enum Foo implements NamedX {
         case Name;
     }

without defining the constant's type just works by the enum case shadowing the interface’s constant it seems consequent to allow `#[\Override]` on enum cases, even if likely not particularly useful.

Best regards
Tim Düsterhus

6

On Tue, Mar 31, 2026 at 2:56 AM Derick Rethans <derick@php.net> wrote:

I think I’m on the " Always reject using #[\Override] on an enum case,
saying that the attribute does not target enum cases" side here, as
mixing class constants with enum cases sounds like a mismatch to me.

cheers,
Derick

On the other hand, if someone is intentionally overriding an interface constant with an enum case, all the more reason that the overriding should be explicitly documented, which is what #[\Override] would do.

-Daniel

7

Hi internals,

I have updated the RFC to resolve the open issue about #[\Override] on enum cases - when marked with #[\Override], the enum case must be overriding an inherited class constant. The fact that this is so uncommon makes it all the more important that when it is intentional, it can be made clear.

This qualifies as a “major change” to the RFC and triggers a 14 day cooldown period.

-Daniel

On Mon, Mar 30, 2026 at 4:36 PM Daniel Scherzer <daniel.e.scherzer@gmail.com> wrote:

Hi internals,

I’d like to start the discussion for a new RFC about adding support for #[\Override] for class constants.

I’d also like to draw specific attention to the open question, which I am soliciting feedback on: how should #[\Override] work for enum cases? See the RFC page for details.

Thanks,
-Daniel

8

Hi internals,

It has been more than 14 days, so the cooldown period is over. Having received no further feedback, this is your official intent to vote message - I plan to open the vote in the next few days if there are no new concerns.

-Daniel

On Sat, Apr 18, 2026 at 6:19 PM Daniel Scherzer <daniel.e.scherzer@gmail.com> wrote:

Hi internals,

I have updated the RFC to resolve the open issue about #[\Override] on enum cases - when marked with #[\Override], the enum case must be overriding an inherited class constant. The fact that this is so uncommon makes it all the more important that when it is intentional, it can be made clear.

This qualifies as a “major change” to the RFC and triggers a 14 day cooldown period.

-Daniel

On Mon, Mar 30, 2026 at 4:36 PM Daniel Scherzer <daniel.e.scherzer@gmail.com> wrote:

Hi internals,

I’d like to start the discussion for a new RFC about adding support for #[\Override] for class constants.

I’d also like to draw specific attention to the open question, which I am soliciting feedback on: how should #[\Override] work for enum cases? See the RFC page for details.

Thanks,
-Daniel