Stdlib: DOMDocument::getElementById() missing — ID lookup fatal (ext/dom/php_dom.c) #14378

Summary

DOMDocument::getElementById(string $elementId): ?DOMElement is part of the ext/dom API in php-src. VM fatals with undefined method DOMDocument::getElementById(); Zend PHP 8.2 in Docker runs the method (returns null when no DTD/id map, or the matching element when configured).

php-src reference

• ext/dom/php_dom.c — dom_document_get_element_by_id
• ext/dom/document.stub.php — DOMDocument::getElementById

PHP implementation target

• ext/dom/VmDom.php + DOM document wrappers (not new C runtime logic)
• Wire libxml ID table when validateOnParse/DTD present; return null when unknown id (Zend parity)

Repro

./script/docker-exec.sh -- php bin/vm.php test/repro/maintainer_gap_dom_get_element_by_id.php
# VM: undefined method DOMDocument::getElementById()
# Zend 8.2: ok (prints null or ok depending on id map)

Expected (php-src-strict)

• Method registered on DOMDocument
• Known id in loaded document → DOMElement; unknown → null
• No fatal for method dispatch

Done when

• Repro green on VM
• ID lookup matches Zend for DTD and non-DTD documents
• Shared VM path; JIT/AOT documented if stubbed