Language: isset() on property hooks must not invoke get hook (zend_property_hooks.c, php-src-strict)

[PurHur]

Category

language · php-src-strict

Problem

On PHP 8.4 property hooks, isset($obj->hooked) must use Zend's isset-style backing probe and must not call the get hook. This compiler invokes the get hook, so virtual/write-only properties with throwing getters fatal instead of returning false.

Distinct from #5203 (get_object_vars() must call get hooks) and from #8732 (json_encode get-hook rule).

Related closed issues that did not cover isset() specifically: #8901 (empty()), #8902 (??).

php-src reference

• php/php-src Zend/zend_property_hooks.c — zend_isset_property_ex
• php/php-src Zend/zend_operators.c — isset opcode on hooked properties

Repro

Save as test/repro/issue_property_hook_isset.php:

<?php
class C {
    public ?string $x {
        get { throw new Exception('get must not run for isset'); }
    }
}
$c = new C();
var_dump(isset($c->x));
echo "ok\n";

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

Runtime	Expected	Observed (2026-06-16)
Zend 8.4+	bool(false) + ok	—
VM	same	Fatal: get must not run for isset

Scope (this repo)

Area	Files
VM	lib/VM.php — issetPropertyHookProbe() / opcode OP_ISSET on hooked props
JIT	lib/JIT/PropertyHookDispatch.php — mirror isset probe without get-hook call
Tests	test/compliance/cases/language/property_hook_isset.phpt

PHP-in-PHP first — no new runtime/*.c branches.

Done when

• Repro prints bool(false) and ok on VM (JIT/AOT when property-hook lowering is in scope)
• Throwing get hook is never invoked for isset($obj->hooked) on virtual/uninitialized hooked properties
• isset() still returns true when separate backing is initialized (php-src-strict)
• Targeted PHPUnit/compliance green; no regressions on Stdlib: get_object_vars() — property hooks must invoke get hook (zend_property_hooks.c) #5203 get-hook paths

Links

• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 self-host · Language: empty() on property hooks must not invoke get hook (zend_property_hooks.c) #8901 / Language: ?? on property hooks must not invoke get hook when backing is initialized (zend_property_hooks.c) #8902 (sibling isset-style ops)

[PurHur]

claim: worker-lane-b — starting this run

[PurHur]

claim: worker-lane-b — starting this run

[PurHur]

Merged via #8925.

Verification (Docker):

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php test/repro/issue_property_hook_isset.php
php vendor/bin/phpunit test/unit/PropertyHookIssetTest.php
php vendor/bin/phpunit test/compliance/VMTest.php --filter "property_hook_isset|property_hook_writeonly_isset|property_hook_empty|property_hook_coalesce"
'

• Issue repro: bool(false) + ok (get hook not invoked)
• Unit + compliance guards green