Language: first-class callable (`strlen(...)`, `Foo::bar(...)`) must yield Closure objects (zend_compile.c)

[PurHur]

Category

language

Problem

PHP 8.1+ first-class callables must be Closure instances (or invokable objects with __invoke), not compile-time string/[class, method] placeholders. This build lowers strlen(...), array_slice(...), and Foo::bar(...) to strings or array pairs, so is_object($f) is false and var_export() shows 'strlen' instead of a Closure::__set_state array.

Related closed tracker #1230 (parse/lowering landed) but runtime zval type still diverges from Zend.

php-src reference

• php/php-src Zend/zend_compile.c — zend_compile_first_class_callable()
• php/php-src Zend/zend_closures.c — zend_create_closure()

Repro

test/tmp/repro-fcc-closure-object.php:

<?php
declare(strict_types=1);
$f = strlen(...);
var_export(is_object($f));
echo PHP_EOL;
var_export($f instanceof Closure);
echo PHP_EOL;

./script/docker-exec.sh -- bash -lc 'php test/tmp/repro-fcc-closure-object.php; php bin/vm.php test/tmp/repro-fcc-closure-object.php'

Check	Zend	This compiler
is_object($f)	true	false
$f instanceof Closure	true	false

Also: array_slice(...) — Zend true, VM false (same lowering).

Scope

Module	Path
Compiler	lib/Compiler.php — compileFirstClassCallable()
VM	Closure / callable object construction
Tests	test/compliance/cases/language/ + JIT when execute probe green

Done when

• strlen(...), static Foo::bar(...), and instance [$o, 'm'](...) FCC forms are Closure (or Zend-equivalent invokable)
• is_callable($fcc) / call_user_func($fcc, ...) parity with Zend on the repro
• ./script/ci-fast.sh --filter first_class (or new compliance case name) green

Related

• Language: first-class callable syntax (Foo::bar(...)) #1230 (closed — syntax/lowering tracker)
• Stdlib: is_callable / call_user_func / call_user_func_array (ext/standard parity) #3132 — is_callable / call_user_func stdlib parity

[PurHur]

claim: cursor-agent-lane-b — starting this run

[PurHur]

Merged via #4961

Verification
```bash
./script/docker-exec.sh -- bash -lc 'php test/tmp/repro-fcc-closure-object.php; php bin/vm.php test/tmp/repro-fcc-closure-object.php'

true / true (Zend) → true / true (VM)

vendor/bin/phpunit --filter first_class_callable_closure_object # OK (2 tests)
```

Function/static FCC are Closure objects on VM+JIT; instance-method FCC still blocked at compile by TypeReconstructor::array() (tracked separately).

[PurHur]

Cleanup: deleting leftover test/tmp/ scratch repro for this closed issue — same coverage lives under test/compliance/cases/ (see PR chore/cleanup-stale-test-tmp-repros).

[PurHur]

Cleanup follow-up: merged #25413 — test/tmp scratch repro removed.