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PHP RFC: Refinements — scoped extension & override methods

  • Version: 0.1
  • Date: 2026-07-01
  • Author: Edd Mann the@eddmann.com
  • Status: Draft
  • Target: PHP 8.5 (experimental fork)
  • Implementation: feature.patch

Introduction

PHP cannot put methods on scalars or arrays, and adding behaviour to a class you do not own means subclassing or global helper functions. Borrowing from Ruby refinements (and Smalltalk/Kotlin extension methods), this RFC adds refinement — a way to add or override methods on any type, including scalars and arrays, that is active only in files which opt in with using. It is the safe monkeypatch: nothing leaks globally and libraries you call never see your changes.

Proposal

refinement Str for string {
    function shout(): string { return strtoupper($this) . '!'; }
}

using Str;
echo "hi"->shout();        // "HI!" — a method call on a scalar
  • Refine scalars & arrays (string, int, float, bool, array), add methods to existing classes, or override existing methods — all scoped.
  • Inside a refinement method, $this is the receiver.
  • A refinement for Base also applies to subclasses.
  • using X; activates a refinement for the rest of the file; resolution follows where a call is written, so a function keeps its refinements when called from elsewhere, and other files do not inherit them.

Implementation

Each refinement R for T { … } method compiles to a plain function under a mangled, NUL-prefixed key, with the receiver injected as the first parameter and $this rewritten to it — so no engine $this-on-a-scalar surgery is needed. using records the refinement in the per-file compile context. In a file with active refinements the compiler rewrites $recv->m(...) to a runtime dispatcher (zend_refinements.c) that looks up a matching active refinement (walking the class hierarchy for objects) or falls back to a normal method call, restoring the caller's scope to preserve visibility. Files that never say using compile and run exactly as before.

Backward Incompatible Changes

  • refinement and using are semi-reserved — still usable as method/constant names.
  • In a using file, every -> call routes through the dispatcher (an opt-in cost for that file only).

Proposed PHP Version(s)

Next PHP 8.x minor.

RFC Impact

  • Opcache: the dispatcher call is emitted only inside opted-in files; other code is unchanged.
  • Scope (v1): one target type per refinement; only -> (not ?->/::); no named arguments to refined calls.

Future Scope

  • Multiple target types per refinement; nullsafe and static-call support.

Proposed Voting Choices

Yes/No, 2/3 majority.

Patches and Tests

  • feature.patch; tests/: refinements — scalar/array/ class refinement, override, add, subclass application, scope isolation across files, and fallback to the normal method.

References

  • Ruby refinements; Kotlin/Smalltalk extension methods.