Re: [PHP-DEV] [DISCUSS] Should RFCs for new functions include a userland polyfill/reference implementation?

Hi  Sepehr

‪Le mar. 25 août 2026 à 13:21, ‫سپهر محمودی‬‎ <[email protected]> a
écrit :‬

> Hi internals,
>
> While reviewing various RFCs that introduce new functions, I noticed an
> inconsistency: some authors include a userland polyfill (reference
> implementation) in their RFCs, while others do not.
>
> I wanted to open a discussion on whether we should strongly encourage RFC
> authors to provide a PHP userland implementation when proposing new
> standard library functions, **where technically feasible**.
>
> Of course, I understand that this isn't possible for every new
> function—especially those that interact with low-level OS APIs, memory
> management, or internal engine features. However, for functions dealing
> with arrays, strings, math, or general logic, I believe this has a couple
> of major benefits:
>
> 1. It clarifies the exact intended behavior, including edge cases and type
> coercions, making the proposal easier to understand without diving into the
> C implementation.
> 2. It immensely helps the community (e.g., the Symfony polyfill team) to
> quickly and accurately port the function to older PHP versions once the RFC
> is accepted.
>
> Should we consider adding this as a standard recommendation (e.g.,
> "Reference Implementation") in the official RFC template for applicable
> functions?
>
> I would love to hear your thoughts on this.
>
> Best regards,
> Sepehr
>
>

In case you didn't know, every polyfill-able feature ends up eventually in
one of the symfony/polyfill-* packages, all centralized in the
https://github.com/symfony/polyfill monorepo.

In my experience, this works quite well and I wouldn't require RFCs to ship
a polyfill: authors should be focused on the C implementation. The PHP
polyfill is not always trivial to achieve, and polyfills proposed in RFCs
don't necessarily end up being the ones shipped via symfony/polyfill, eg
because edge cases or perf improvements.
Polyfill needs a separate workflow.

Cheers,
Nicolas