Regression: property hooks + explicit backing — spurious Cannot redeclare when sibling property sits between hook and backing (re-#9673, Zend/zend_compile.c) #16936

Category

language · property hooks · php-src-strict

Problem

Valid PHP 8.4 classes with a hooked property, an unrelated sibling property, and an explicit private backing field for the hook compile on Zend but fail here with Cannot redeclare C::$x.

Discovered via maintainer VM scan (test/repro/maintainer_gap_property_hook_multi_property_redeclare.php). Regression of #9673 — closed 2026-06-18 but repro red again on master with PHP_COMPILER_PROFILE=8.4.

php-src reference

• php/php-src Zend/zend_compile.c — hooked property + backing field registration (zend_compile_property_hook)

PHP implementation target

• lib/Compiler.php / property-hook decl collector — do not treat explicit backing $x as a duplicate symbol when a sibling property is declared between the hook and backing field
• Parser/lowering only; no runtime/*.c expansion

Repro

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && export PHP_COMPILER_PROFILE=8.4 && php bin/vm.php test/repro/maintainer_gap_property_hook_multi_property_redeclare.php'
# parseAndCompile failure: Cannot redeclare C::$x

Minimal inline repro:

class C {
    public int $x { get => $this->x; set => $this->x = $value; }
    public string $y = 'a';
    private int $x = 1;
}

Done when

• maintainer_gap_property_hook_multi_property_redeclare.php prints compile-ok x=1 y=a
• Compliance .phpt under test/compliance/cases/language/property_hooks/
• php-src-strict; VM/JIT/AOT agree