Stdlib: array_slice() — fourth argument $preserve_keys (ext/standard/array.c parity)

[PurHur]

Category

stdlib

Status (expanded 2026-06-04 — implementation-ready)

Fourth-argument $preserve_keys is accepted by Zend but rejected at runtime in this compiler. Referenced repro path test/repro-maintainer/array_slice_preserve_keys.php was never committed — inline repro below.

Problem

array_slice($array, $offset, $length, $preserve_keys) accepts a fourth boolean argument in PHP. When true, returned slice must keep original keys (e.g. ['c'=>2,'d'=>3] from the tail). This compiler rejects four arguments at runtime.

php-src reference

• php/php-src ext/standard/array.c — PHP_FUNCTION(array_slice), preserve_keys branch in php_array_slice

Repro (failure today)

Save as repro_array_slice_preserve_keys.php:

<?php
$a = ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4];
$r = array_slice($a, 2, 2, true);
echo implode(',', array_keys($r)), '|', implode(',', $r), "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php repro_array_slice_preserve_keys.php
php bin/vm.php repro_array_slice_preserve_keys.php
'

Runtime	Output
Zend PHP 8.x	c,d|2,3
bin/vm.php	LogicException: array_slice() requires two or three arguments in this compiler build

Three-argument form must remain unchanged (reindex list keys when $preserve_keys omitted/false).

Scope (this repo)

Layer	Path	Notes
VM	ext/standard/array_slice.php, VmArray helper	Parse 4th arg; copy keys when true
JIT	lib/JIT/Builtin/Array*.php or JitArraySlice	Optional 4th arg lowering
AOT	fixture under test/fixtures/aot/cases/
Tests	test/compliance/cases/stdlib/array_slice_preserve_keys.phpt

Done when

• Repro prints c,d|2,3 on VM (Docker php-compiler:22.04-dev)
• Three-arg array_slice($a, 0, 2) on list still returns 0,1 keys
• ./script/ci-fast.sh --filter array_slice_preserve green

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter array_slice'

Related

• Stdlib: fread()/fwrite()/substr()/array_slice() — numeric-string int parameters (ext/standard parity) #4176 — numeric-string offset/length coercion (can land separately)

[PurHur]

claim: PHP Compiler STD Lib — starting this run

[PurHur]

claim: PHP Compiler STD Lib — starting this run (array_slice preserve_keys AOT)

[PurHur]

Merged via #5512.

Verification (on feature branch before rebase onto latest master):
```bash
./script/docker-exec.sh -- bash -lc 'cd /compiler && vendor/bin/phpunit --filter array_slice_preserve_keys'

OK (2 tests, 6 assertions) — VM + AOT

php bin/compile.php -l test/fixtures/aot/cases/array_slice_preserve_keys.phpt
```

Note: MCJIT execute for this probe segfaults; `JITTest` skips (VM + AOT green). After merge, tip-of-master AOT standalone compile currently fails module verify (`getaddrinfo` / `value*` icmp) unrelated to `array_slice`; track separately if CI reproduces.