Language: readonly property with hooks — compile rejects valid PHP 8.4 pattern (Zend/zend_compile.c)

[PurHur]

Category

language · php-src-strict · PHP 8.4 property hooks

Problem

PHP 8.4 allows readonly properties with set hooks initialized from the constructor (hook writes during object construction):

class C {
    public readonly int $x {
        get => $this->x;
        set { $this->x = $value; }
    }
    public function __construct() {
        $this->x = 0;
    }
}
$c = new C();
$c->x = 1; // runtime Error after init

This compiler rejects at compile:

Hooked properties cannot be readonly

Maintainer repro: test/repro/maintainer_gap_readonly_hook_write_exception.php.

php-src reference

• php/php-src Zend/zend_compile.c — readonly + hook validation
• php/php-src Zend/zend_property_hooks.c — set hook during construction vs post-init write Error

Repro

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

Engine	Compile	Runtime write after construct
Zend PHP 8.4+	OK	catchable Error (not compile fail)
VM today	compile fail	n/a

Scope

• lib/Compiler.php — allow readonly + hooks; enforce post-construct write rules at runtime
• lib/VM.php — set hook + readonly interaction
• test/compliance/cases/language/readonly_property_hook.phpt

Done when

• Repro compiles on VM
• Post-construct $c->x = 1 throws catchable Error matching Zend message class
• Constructor init via set hook succeeds
• ./script/ci-fast.sh --filter readonly_property_hook green

Related

• Language: unset() on get-only property hook — must Error before unset, not read-only property conflation (Zend/zend_property_hooks.c) #9800 unset get-only · Language: static property hooks — PHP 8.4 parse + get/set dispatch (Zend/zend_compile.c) #9725 static hooks · #1492

[PurHur]

claim: cursor-agent-lane-c — starting this run

[PurHur]

claim released: php-src master zend_compile.c still emits compile error Hooked properties cannot be readonly (line ~8952); PHP manual + property-hooks RFC agree readonly + hooks are incompatible in PHP 8.4. Current compiler matches php-src-strict. Pivoting to another lane-C issue.

[PurHur]

claim: cursor-agent-lane-b — starting this run

[PurHur]

claim: cursor-agent-lane-b — continuing this run (readonly property with hooks compile allow)

[PurHur]

claim released: php-src-strict — PHP 8.4 manual + property-hooks RFC explicitly disallow readonly + hooks (compile error). Current VM matches #9805 compliance PHPTs. Issue acceptance contradicts Zend reference; recommend close as invalid.

[PurHur]

claim: cursor-agent-lane-b — continuing this run (readonly property with hooks compile allow)

[PurHur]

claim: cursor-agent-lane-b — verification run (no code change)

php-src-strict verdict: issue acceptance contradicts Zend / closed #9805

Evidence:

1. PHP 8.4 property hooks RFC: "a readonly property with a get or set hook is disallowed and will throw a compile error"
2. PHP manual: "Property hooks are incompatible with readonly properties"
3. Closed Language: property hook + same-name backing field — must parse-error (Zend/zend_compile.c) #9805 explicitly scoped rejecting readonly+hooks; compliance PHPTs readonly_property_hook_set.phpt expect compile fatal
4. PropertyHooksTest::testReadonlyHookedPropertyCompileErrors guards current behavior

Current VM compile rejection (Hooked properties cannot be readonly) is correct. Recommend close as invalid/duplicate of #9805.

Releasing claim — no PR.

[PurHur]

claim: cursor-agent-lane-b — verification run (no code change)

php-src-strict: issue acceptance contradicts Zend / RFC / manual (re-confirmed 2026-06-20)

Evidence:

1. Property hooks RFC — Interaction with readonly: "a readonly property with a get or set hook is disallowed and will throw a compile error"
2. PHP 8.4 manual: "Property hooks are incompatible with readonly properties"
3. VM correctly rejects test/repro/maintainer_gap_readonly_hook_write_exception.php with Hooked properties cannot be readonly (php-src-strict match)
4. Closed Language: property hook + same-name backing field — must parse-error (Zend/zend_compile.c) #9805 + compliance PHPTs expect this compile fatal

Docker env has PHP 8.2.31 (no hook syntax); VM compile rejection matches expected php-src behavior for readonly+hooks.

Recommend close as invalid/duplicate of #9805 — implementing done-when would regress php-src parity.

Releasing claim — no PR.

[PurHur]

claim: cursor-agent-lane-b — starting this run