Re: [Pre-RFC] Scalar object methods (with a working implementation)

On Tue, Jun 30, 2026, at 00:32, Michal Kral wrote: > Hi all, > > Per Seifeddine's suggestion to keep this out of the karma-request > thread, I'm opening a pre-RFC discussion for scalar object methods -- > calling a small, curated set of methods directly on scalar values, e.g.. > $str->trim(), (3)->pow(2). There's a complete, tested implementation and > a full write-up (links below); I'd like to surface the strongest > objections before I write the formal RFC. > > Disclosure: I built this with an AI assistant (Claude) as a tool. The > design and the decisions are mine, and I've independently verified the > engine behaviour, performance, JIT correctness, leak-freedom and the BC > scan. Flagging it up front for transparency. > > I know "methods on primitives" was proposed and declined before > (Nikita's 2014 "Methods on primitive types in PHP"). The reason it > stalled was loose typing: $x->trim() would need a runtime type check and > would behave differently depending on what $x held. This proposal > sidesteps that entirely, by generalizing the resolution Nikita himself > suggested in that thread -- requiring an explicit cast where the type > isn't already clear. > > The idea: dispatch only on receivers the compiler already knows are > scalar. The method call is rewritten at compile time to an ordinary call > into an internal backing class -- no runtime type dispatch, no new > opcode, the object method-call path is untouched. A receiver qualifies > only if its type is guaranteed syntactically: a literal, a > (string)/(int) cast, a concatenation/interpolation, a non-nullable > scalar-typed property, or a call with a declared non-nullable scalar > return type. An untyped $x->trim() is left exactly as today (Error). > Crucially, dispatch never depends on optimizer-inferred types, so > behaviour is identical with and without opcache. > > echo " Hello World "->trim()->upper(); // "HELLO WORLD" > echo (3)->pow(2); // 9 > echo "hello"->length()->pow(2); // 25 -- length():int > chains into the int methods > > So the cast Nikita proposed, ((string) $num)->chunk(), is only needed > where the type isn't already guaranteed; everywhere else the dispatch is > sound by construction, with no runtime check. > > It's intended as one proposal with two independent votes: > > 1. Scalar methods on guaranteed free receivers (the above). A pure > capability -- it adds a way to call scalar operations and changes > nothing about untyped code. Proposed initial sets: a small curated Str > (trim/upper/lower/length + contains/startsWith/endsWith), Int > (abs/pow/clamp), and Float (round/ceil/floor/abs); bool deliberately > gets none (its operations are operators, not methods). The sets are > governed by explicit criteria and are the easiest thing to tune in > discussion. > > 2. Scalar-typed local variables (int $x = ...;, scalar types only), > which additionally make a typed local a guaranteed receiver (string $s = > ...; $s->trim()). This is the more contested half -- it also carries the > "local type discipline" argument -- so it's a separate vote: a "no" > here > ships the capability without typed locals. > > What I'm deliberately NOT doing, up front so it's not a surprise: > > - No method-call-result receivers ($this->getName()->trim()) -- that > would rest on return-type covariance under inheritance; not worth the > surface. > - Int::abs/pow return int|float (they can overflow, as the global > functions do), so they're honest terminals -- they don't chain. > (Int::clamp is the one initial int method provably :int for all inputs, > so it does chain.) > - No int|false typed locals -- that's a sentinel state, not a committed > type; ?T is supported, sentinel-unions are not. > - The backing classes are internal-only (NUL-prefixed name, like > anonymous classes): class_exists('Str') is false, no Reflection, > userland "class Str {}" can't collide. > > Implementation status -- this is built and tested, not a sketch: > > - Scalar methods add zero new opcodes -- the desugar emits an ordinary > static call, and the object method-call path is byte-for-byte unchanged. > (Typed locals add dedicated *_TYPED assignment opcodes, but the untyped > hot path stays byte-identical.) > - Performance (deterministic callgrind, release build): the untyped hot > path is byte-identical; the standard bench.php suite is +0.145% > instructions, entirely from predicted-not-taken branches in reference > opcodes only, with zero added cache misses or branch mispredictions. A > typed-local write benchmarks at ~0.79x the cost of a typed-property > write -- a check the language already runs on every typed-property write > since 7.4. > - References (the objection that sank prior typed-locals attempts) are > enforced through every path -- =&, by-ref params, > array/object/static-prop refs, yield, closure capture, $$name, extract, > $GLOBALS, global -- via the existing typed-property reference machinery. > Leak-checked under stress. > - Correct under JIT in all three modes (interpreter, function, tracing > -- differential byte-identical output). opcache SHM + file_cache > round-trip verified. > - BC impact, measured: an AST scan of the 1,000 most-downloaded > Packagist packages (173k+ files) found zero method-call sites with a > guaranteed-scalar receiver -- i.e. zero call sites that change behaviour > (every such site is a fatal error today). Userland Str classes (incl. > Laravel's Illuminate\Support\Str) coexist with the backing class, verified. > > Full write-up (RFC draft, plus the method-set, performance, and > BC-impact analyses): > > https://github.com/kralmichal/php-src/tree/rfc/docs/scalar-object-methods-rfc > > Implementation branches (PHP 8.6-dev base): > - Primary (scalar methods): > https://github.com/kralmichal/php-src/tree/rfc/scalar-methods > - Secondary (typed locals, stacked): > https://github.com/kralmichal/php-src/tree/rfc/typed-locals > > What I'd value discussing before I write the formal RFC: > > 1. Does the "compile-time-guaranteed receivers only" framing actually > resolve the loose-typing objection, or is there a hole I'm not seeing? > 2. The method-set and naming is the most open part -- is a small > curated, clean-slate set (distinct from the procedural names) the right > direction, or a non-starter? How should it relate to the existing > userland efforts in this space (e.g. Psl)? > 3. Anything that would sink this before I invest in the full RFC. > > Thanks, > Michal Kral > Hi Michal, This is the part that gets me: > requiring an explicit cast where the type isn't already clear. Explicit casting in PHP is *dangerous*: (int) "123password" === 123 https://3v4l.org/IAF8W — Rob