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Regression: final class constants can be overridden by child class (re-#4455, Zend/zend_inheritance.c) #22329
Description
Category
bug · php-src-strict · language · final class constants
Problem
PHP 8.1+ final const on a class must refuse child redeclaration. After #4455, parse accepts final const, but inheritance still allows override — Zend fatals at compile/eval time.
Verified 2026-07-22 on af276f464 (host PHP 8.2.32 Zend vs php bin/vm.php):
| Repro | Zend 8.2 | VM |
|---|---|---|
class A { final public const X = 'a'; } eval('class B extends A { public const X = \"b\"; }') |
Fatal: B::X cannot override final constant A::X |
override allowed, B::X=b |
Same under PHP_COMPILER_PROFILE=8.4.
php-src reference
- php/php-src
Zend/zend_inheritance.c— class constant override /ZEND_ACC_FINAL - php/php-src
Zend/zend_compile.c—finalbit onZEND_AST_CLASS_CONST_GROUP - Prior: Language: final class constants (final const) — parse + override rules (zend_compile.c parity) #4455 (closed — parse shipped; override enforcement still red)
PHP implementation target
lib/Compiler.php/ inheritance checks — reject child const when parent const is final (compile-time)lib/VM.phpclass-entry merge — same guard if constants register at runtime/eval- Prefer PHP-in-PHP; no new
runtime/*.c
Repro
./script/docker-exec.sh -- bash -lc 'php bin/vm.php -r '"'"'class A { final public const X = \"a\"; } eval(\"class B extends A { public const X = \\"b\\"; }\"); echo B::X, \"\n\";'"'"''Done when
- Child redeclaration of
final constfatals like Zend (cannot override final constant) - Works for
evaland normal compile;ReflectionClassConstant::isFinal()stays true - Compliance
.phptundertest/compliance/cases/; php-src-strict; no php-compiler-strict shortcut
Activity
PurHur commentedon Jul 22, 2026
claim: Worker lane A — starting this run
Pre-triage gates (this workspace):
Language: reject eval override of final class constants (#22329) (#22342
PurHur commentedon Jul 22, 2026
Merged via #22342
Verification:
eval('class B extends A { public const X = "b"; }')afterfinal public const Xnow fatals withB::X cannot override final constant A::X(exit 255).ReflectionClassConstant::isFinal()remains true. Guard lives in VMinheritFromParent/inheritFromInterfaces(rejectChildOverrideOfFinalClassConst). Compliance:final_class_const_eval_override.phpt; unit:FinalClassConstCheckTest::testEvalCannotOverrideFinalClassConstant.Pre-triage:
release-readiness --json→user_release_ready: yes; AOT smoke red on master independently (not this change).