Language: property hooks in interfaces — concrete property must satisfy interface { get; } (PHP 8.4, zend_compile.c)

[PurHur]

Category

language

Problem

PHP 8.4 allows property hooks in interface declarations, e.g. public string $label { get; }. A implementing class may satisfy the get hook with an ordinary typed property (public string $label = 'hi';) without declaring an explicit hook body.

This compiler parses the interface, but rejects valid implementations:

Class C contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (C::$label::get)

php-src reference

• php/php-src Zend/zend_compile.c — interface property hooks / abstract hook validation
• php/php-src Zend/zend_property_hooks.c
• PHP RFC: Property hooks in interfaces (8.4)

Repro (failure today)

<?php
interface I {
    public string $label { get; }
}
class C implements I {
    public string $label = 'hi';
}
$c = new C();
echo $c->label, "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php repro.php
# Compare on PHP 8.4+ reference build when available
'

Observed (VM): compile-time abstract-method fatal for C::$label::get.

Expected (php-src 8.4): compiles; prints hi.

Implementation hints (PHP-in-PHP)

• Teach interface/class compatibility in compiler + PHPCfg: a concrete typed property with matching visibility/type satisfies an interface { get; } (and { set; } where applicable) without an explicit hook body.
• Align with existing property hook lowering in lib/SourcePreprocessor/PropertyHooks.php and VM dispatch in lib/VM.php.
• Compliance: test/compliance/cases/language/interface_property_hooks.phpt.

Pairs

• Language: property hooks without set — assignment must throw Error (zend_property_hooks.c) #4821, Stdlib: get_object_vars() — property hooks must invoke get hook (zend_property_hooks.c) #5203 (property hook runtime)
• Stdlib: ReflectionProperty::isVirtual()/isDynamic()/getHooks() — PHP 8.4 property hook reflection missing (php_reflection.c) #7295 (ReflectionProperty hook introspection)

Done when

• Repro compiles on VM and prints hi (no abstract-method fatal for C::$label::get)
• Class that omits the property or declares incompatible type/hook still compile-fatals with php-src-aligned message
• Interface with { get; set; } and implementing class with matching typed property + implicit hooks still works
• ./script/ci-fast.sh --filter interface_property_hooks green
• No new C runtime branches

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter interface_property_hooks'
php bin/vm.php test/repro/maintainer_interface_property_hooks.php
php bin/vm.php test/repro/maintainer-interface_property_hooks.php 2>/dev/null || true

Strictness

php-src-strict — default CI/compliance must match PHP 8.4 Zend interface hook satisfaction rules.

[PurHur]

claim: Worker Lane C — starting this run

[PurHur]

Merged via #7335.

Verification:

• ./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter interface_property_hooks' → OK
• ./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php test/repro/maintainer_interface_property_hooks.php' → prints 1 and home
• Issue repro (interface I { public string $label { get; } } + class C implements I { public string $label = 'hi'; }) → prints hi

Plain typed properties on implementing classes now satisfy interface { get; } / { get; set; } without abstract-method fatals.