Language: isset()/empty() on property-hook virtual properties — get-hook semantics (zend_object_handlers.c parity) #4586

Category

language

Problem

Property hooks (get / set) lower and dispatch on normal reads/writes (#3145, #3723), but isset($obj->prop) and empty($obj->prop) on hook-only virtual properties do not invoke the get hook. VM uses objectPropertyIsSet() which only inspects raw storage + __isset magic — it never calls fetchPropertyWithHooks().

Zend PHP 8.4+ treats hooked properties like real properties for isset/empty (get hook invoked; result checked for null/undefined).

php-src reference

• php/php-src Zend/zend_object_handlers.c — zend_std_has_property, hooked property isset path
• php/php-src Zend/zend_compile.c — property hook metadata
• Manual: property hooks + isset/empty behavior

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 repro.php'
php repro.php

Minimal get-only hook:

<?php
class R {
    public int $n { get => 42; }
}
$r = new R();
var_export(isset($r->n), empty($r->n));

Scope (this repo)

Do not permanently stub with internal_*; invoke get hook like normal fetch, then apply isset/empty rules to returned value.

Done when

• Repro output matches Zend on VM for hooked properties (with and without backing field)
• JIT/AOT compile + execute same results (bin/jit.php repro.php)
• ./script/ci-fast.sh --filter property_hook_isset green
• No regression on plain properties / __isset magic (Language: isset($obj->prop) on undefined property — return false (Zend zend_operators.c parity) #3603)

Related

• Language: PHP 8.4 property hooks — get/set on properties (Zend parity) #3145 property hooks VM · Language: readonly property hooks — set hook cannot assign to readonly backing store outside __construct (zend_compile.c) #4518 readonly hook set guard · Language: Property hooks JIT/AOT lowering (phase 2 of #3145) #3723 JIT dispatch
• North star: Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492