Arrays: Full associative array support (string keys, holes, rehash)

[PurHur]

Problem

HashTable has packed-list fast paths; several methods throw for non-packed arrays (mergeCopy, sliceCopy, etc.). rehash() throws LogicException('Need to implement rehash') in lib/VM/HashTable.php (~L908).

Web apps use string-keyed maps ($_GET, config arrays, JSON-decoded data). Self-host M3 native emit segfaults in __hashtable__readStringKeyValue (#1514) — tracked as critical-path child #1761.

Goal

Reliable associative arrays for VM, JIT, and native AOT hashtable runtime.

Implementation hints

Layer	Files	Notes
VM rehash	lib/VM/HashTable.php	Replace throw; grow indexes/buckets MaskedArrays; preserve string + int keys
Packed → mixed	same	Triggers on first string key or hole
JIT	lib/JIT/Builtin/ hashtable helpers	String-key get/set after VM rehash
AOT runtime	native __hashtable__* stubs	Align with VM semantics for self-host bundle
Methods	mergeCopy, sliceCopy, array_merge paths	Un-skip or document assoc limits

Repro (VM)

$a = [];
for ($i = 0; $i < 20; $i++) {
    $a["key$i"] = $i;  // triggers rehash today → LogicException
}
echo $a['key19'];

Tests

• test/compliance/cases/hashtable_rehash.phpt — insert until rehash, read back
• test/compliance/cases/hashtable_string_keys.phpt — isset/unset on string keys
• Optional @group llvm AOT fixture mirroring VM script

Tasks

• Implement rehash for mixed key types (Self-host M3: HashTable rehash for native AOT runtime (#66 → #1514) #1761 M3 blocker)
• JIT: string-key get/set on __hashtable__ (partially used for superglobals)
• Enable array_merge, array_slice on assoc arrays or document limits
• PHPT regression suite for string keys, unset, isset

Acceptance criteria

./phpc run -r '$config = ["db" => "localhost", "port" => "3306"]; echo $config["db"];'
# → localhost (no LogicException)

./script/ci-fast.sh --filter hashtable

$config = ['db' => 'localhost', 'port' => '3306']; operations work in VM+JIT without LogicException.

Dependencies

• Self-host M3: HashTable rehash for native AOT runtime (#66 → #1514) #1761 — M3 native emit blocked on rehash / hashtable ABI
• M3: Native HelloWorld runtime segfault in __hashtable__readStringKeyValue (helloworld_compile_smoke) #1514 — segfault symptom
• Language: array_map() JIT/AOT parity (stdlib subset for web helpers) #542 — array_map on assoc arrays

Verification (local / Docker only)

./script/ci-fast.sh --filter hashtable
docker run --rm -v "$(pwd):/compiler" -w /compiler php-compiler:22.04-dev ./script/ci-fast.sh --filter hashtable

No GitHub Actions (#394 ✅).

Links

• ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 Phase 1 Language / Phase 5 Self-host
• Epic Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492