Regression: DOMDocument::getElementById() with duplicate setIdAttribute ids — Zend first wins, VM last (ext/dom/document.c)

[PurHur]

Category

bug · php-src-strict · DOM ID map · pillar 4

Problem

When two elements share the same id attribute and both call setIdAttribute('id', true), Zend getElementById() returns the first element in document order; VM returns the last. Probed 2026-07-30 vs Zend 8.2.32.

Repro	Zend 8.2.32	VM (2026-07-30)
<a id="x"/><b id="x"/> both setIdAttribute; getElementById('x')->nodeName	a	b

php-src reference

• php/php-src ext/dom/document.c — getElementById / ID hashtable (first registration wins)
• php/php-src ext/dom/element.c — setIdAttribute

PHP implementation target

• ext/dom/ ID-map — do not overwrite an existing id entry on a second setIdAttribute (match Zend first-wins); PHP-in-PHP

Repro

./script/docker-exec.sh -- bash -lc '
php test/repro/maintainer_gap_dom_getelementbyid_duplicate_setidattribute.php
php bin/vm.php test/repro/maintainer_gap_dom_getelementbyid_duplicate_setidattribute.php
'

Inline:

$d = new DOMDocument();
$d->loadXML('<r><a id="x"/><b id="x"/></r>');
$a = $d->documentElement->firstChild;
$b = $a->nextSibling;
$a->setIdAttribute('id', true);
$b->setIdAttribute('id', true);
echo $d->getElementById('x')->nodeName, "\n";
// Zend: a  VM: b

Done when

• Duplicate setIdAttribute → getElementById returns first element on VM (+ JIT/AOT when in scope)
• Compliance .phpt + keep test/repro/maintainer_gap_dom_getelementbyid_duplicate_setidattribute.php
• php-src-strict; no php-compiler-strict shortcut

[PurHur]

claim: PHP Compiler Ext — DOM & XML — starting this run (cohesive with #25274 — same ID-map first-wins / detach semantics)

[PurHur]

Merged via PR #25341 (with #25274).

Fix: registerElementId / document-order index no longer overwrite an existing ID slot — matches xmlAddID first-wins. Duplicate setIdAttribute → getElementById returns the first element.

Verified: Zend/VM/JIT test/repro/maintainer_gap_dom_getelementbyid_duplicate_setidattribute.php → a.

[PurHur]

Closed by PR #25341 (squash commit included #25275; closing explicitly).