PHP RFC: Final anonymous classes

• Date: 2023-11-15
• Author: Daniil Gentili daniil@daniil.it
• Status: Under Discussion

This RFC proposes to add support for final anonymous classes, or make all anonymous classes final by default, with or without the possibility to make them non-final.

This RFC proposes to either add support for final anonymous classes, or make all anonymous classes final by default, with or without the possibility to make them non-final.

This should also allow some additional opcache optimizations, such as any JIT logic gated behind a check on ZEND_ACC_FINAL, i.e. https://github.com/php/php-src/blob/master/ext/opcache/jit/zend_jit_trace.c#L4507.

None.

Next PHP 8.4

See Backward Incompatible Changes.

2/3 required to accept.

Add support for final anonymous classes?
Real name	Yes	No
alcaeus (alcaeus)
alec (alec)
ashnazg (ashnazg)
brzuchal (brzuchal)
crell (crell)
cschneid (cschneid)
derick (derick)
devnexen (devnexen)
dharman (dharman)
galvao (galvao)
geekcom (geekcom)
heiglandreas (heiglandreas)
kalle (kalle)
kguest (kguest)
levim (levim)
mbeccati (mbeccati)
nicolasgrekas (nicolasgrekas)
nielsdos (nielsdos)
nikic (nikic)
ocramius (ocramius)
ramsey (ramsey)
sebastian (sebastian)
stas (stas)
weierophinney (weierophinney)
Final result:	8	16
This poll has been closed.

Final anonymous classes implementation: https://github.com/php/php-src/pull/11126

• Pull request discussion: https://github.com/php/php-src/pull/11126
• Internals discussion: https://externals.io/message/121356

Personally, I would have instead preferred the much cleaner approach of making all anonymous classes final by default, (preferrably) without offering the option to make them non-final.

However, I understand that this might be a little bit too restrictive for something that may have some valid usecases, even if extending anonymous classes currently requires some hack-ish workarounds with class_alias.

Thus, this RFC initially included three mutually exclusive proposals:

1. Add support for final anonymous classes (new final class {} syntax, no breaking changes)
2. OR Make all anonymous classes final by default, without the option to make them final (breaking change)
3. OR Make all anonymous classes final by default, provide an optional open keyword to make them non-final (like in Kotlin, new open class {}, breaking changes).

As an extra proposal related to the last two options, possibly requiring a separate RFC, in the last two cases, it might be a good idea to also disallow the use of class_alias altogether for final anonymous classes (suggested by nikolas-grekas in https://github.com/php/php-src/pull/11126#issuecomment-1522042841).