Stdlib: unpack() — enum case operands must warn+pack backing int like Zend (ext/standard/pack.c, php-src-strict)

[PurHur]

Category

stdlib

Problem

unpack() (and enum operands passed into pack() for the data buffer) do not match Zend when a backed enum case is used where an int/string scalar is expected. Zend emits a Warning: Object of class E could not be converted to int and proceeds using the backing value. This compiler fatals via VmJson::export / unsupported value type (verified 2026-06-05).

Related: #5713 tracks pack() enum behavior; this issue covers unpack() and the full pack/unpack pipeline.

php-src reference

• php/php-src ext/standard/pack.c — php_pack, php_unpack, scalar coercion with zend_try_numeric / object-to-scalar warnings

Repro (verified 2026-06-05)

<?php
enum E: int { case A = 1; }
$data = pack('c', E::A);
var_dump(unpack('c', $data));

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

Step	Zend PHP 8.2	bin/vm.php (today)
pack('c', E::A)	Warning + packs byte 0x01	Warning path differs; may fatal ❌
unpack('c', $data)	array(1 => int(1))	VM fatal: json_encode() value type not supported ❌

Direct enum into unpack format args should also TypeError per Z_PARAM_STR on format string — test separately.

Scope (PHP-in-PHP)

Path	Change
ext/standard/unpack.php, ext/standard/pack.php	scalar coercion via VmPack / UnpackEngine — enum case → backing with Zend warning
ext/standard/VmPack.php, UnpackEngine.php	never route enum cases through VmJson::export
lib/JIT/Builtin/JitUnpack.php, JitPack.php	mirror coercion when JIT lowered
Tests	test/compliance/cases/stdlib/unpack_enum_case.phpt, extend pack_enum_case.phpt

Done when

• Repro script matches Zend output on VM (warning + correct unpacked int)
• No VM fatal / abort on enum-backed pack/unpack round-trip
• JIT/AOT compliance when issue requires MCJIT/AOT paths
• Cross-link Stdlib: pack() on backed enum operands — must warn and pack backing int, not VmJson::export fatal (ext/standard/pack.c) #5713 closed or narrowed when both green

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter unpack_enum'
./script/ci-fast.sh --filter UnpackEnum

Links

• Stdlib: pack() on backed enum operands — must warn and pack backing int, not VmJson::export fatal (ext/standard/pack.c) #5713 pack() enum · Stdlib: hash()/hash_hmac()/md5()/sha1()/crc32() — enum case operands must TypeError (ext/hash, ext/standard) #5780 php-src-strict hash family · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 self-host

[PurHur]

claim: PHP Compiler STD Lib — starting this run

[PurHur]

Merged via #7911.

Verification

• `php test/repro/issue_6213_pack_unpack_enum.php` and `php bin/vm.php …` — Zend-matching warning + `array(1=>int(1))` round-trip
• `vendor/bin/phpunit --filter "pack_backed_enum|pack_enum_string|unpack_enum"` — 6/6 green (VM + JIT)
• `php bin/compile.php -l test/repro/aot_pack_backed_enum.php` — exit 0

Also closes the pack() half of #5713 (string-format enum → `Error`).