Language: property hooks — isset() and empty() must use get hook (zend_property_hooks.c) #4701

Category

language

Problem

PHP 8.4 property hooks: isset($obj->prop) and empty($obj->prop) on a hooked property must run the get hook (or Zend-equivalent logic) before testing definedness, not only read raw backing storage. This compiler has get/set hook dispatch on fetch/store (lib/VM.php fetchPropertyWithHooks) but objectPropertyIsSet() may disagree with Zend when the backing field is unset and only the get hook supplies a value.

Repro sketch: test/repro-maintainer/property_hook_isset.php.

php-src reference

• php/php-src Zend/zend_property_hooks.c — isset / empty on hooked properties
• php/php-src Zend/zend_object_handlers.c — zend_std_has_property

Repro

<?php
class Box {
    public string $label {
        get => strtoupper($this->label);
        set (string $v) { $this->label = $v; }
    }
    public function __construct() { $this->label = 'hi'; }
}
$o = new Box();
var_export(isset($o->label));
echo "\n";
var_export(empty($o->label));
echo "\n";

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

Add a get-only case (no set hook) per #4687 when that lands.

Scope

• lib/VM.php — objectPropertyIsSet, empty() lowering on property fetches
• lib/SourcePreprocessor/PropertyHooks.php — hook method names
• lib/JIT/PropertyHookDispatch.php — JIT isset/empty (phase 2 OK to defer)
• test/compliance/cases/language/property_hook_isset_empty.phpt

Done when

• Repro matches Zend on VM for isset + empty
• Get-only hooked property: isset follows get hook (Language: property hooks — get-only virtual properties without set hook (zend_property_hooks.c) #4687)
• ./script/ci-fast.sh --filter property_hook_isset green

Links

• Language: PHP 8.4 property hooks — get/set on properties (Zend parity) #3145 property hooks · Language: property hooks — get-only virtual properties without set hook (zend_property_hooks.c) #4687 get-only hooks · Language: isset()/empty() on property-hook virtual properties — get-hook semantics (zend_object_handlers.c parity) #4586 isset parity · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492