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Date: Sat, 15 Jun 2024 12:16:21 +0100
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Subject: [PHP-DEV] Static class
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From: bilge@scriptfusion.com (Bilge)

Hi Internals,

I want to introduce the `static` keyword at the class declaration level. 
That is, the following would be valid: `static class Foo {}`.

A "static class" is one that only permits static members 
(methods/properties) and could have similar semantics to a static class 
in C# 
<https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/static-classes-and-static-class-members>. 
In particular: static classes are implied final and they cannot inherit 
from any other class. These specific semantics are negotiable, but in 
practice I've never seen the need to mix inheritance with pure static 
classes.

A static class can be emulated somewhat with a trait in userland, and I 
have long used such a micro library for this purpose 
<https://github.com/ScriptFUSION/StaticClass/blob/master/src/StaticClass.php>. 
This works by forcing the constructor to be private, thus preventing 
instantiation, but it cannot guarantee that the consumer does not create 
any instance methods anyway (just that such methods would be useless as 
they would be inaccessible). Ergo, it would be better to have this as a 
language feature so the compiler can provide the necessary guarantees 
and warnings against improper use.

I am not too familiar with internals, but I figure I can probably muddle 
my way through an implementation by following the readonly PR 
<https://github.com/php/php-src/pull/7305/files>, which I imagine has 
similar touch points. The main thing I'd like to ascertain at this stage 
is whether such a PR would have support?

Kind regards,
Bilge