php-in-php: DOMImplementation — createDocument/createDocumentType without host DOM (ext/dom/php_dom.c)

[PurHur]

Category

php-in-php | stdlib

Problem

DOMImplementation is the factory for empty DOM trees (createDocument, createDocumentType, hasFeature). It is required for XML generation without parsing input and is referenced by php-types stubs. This compiler has no DOM surface (#3326 tracks DOMDocument generally); class_exists('DOMImplementation') is false (Jun 2026 audit).

Implementing DOMImplementation first establishes the document factory path that DOMDocument / DOMElement build on.

php-src reference

• ext/dom/php_dom.c — dom_domimplementation_class_entry, dom_implementation_create_document
• ext/dom/php_dom.stub.php — DOMImplementation::createDocument, createDocumentType, hasFeature
• ext/dom/dom_ce.h — class registration

Repro (failure today)

<?php
$impl = new DOMImplementation();
$doctype = $impl->createDocumentType('html', '-//W3C//DTD HTML 4.01//EN', 'http://www.w3.org/TR/html4/strict.dtd');
$doc = $impl->createDocument(null, 'html', $doctype);
$doc->formatOutput = true;
echo $doc->saveXML();

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

Runtime	Output
Zend PHP 8.x (dom)	XML string with <!DOCTYPE html> + <html>
bin/vm.php	fatal — class DOMImplementation not found

Scope (this repo)

Area	Path	Notes
Module	ext/dom/ (new)	PHP class handlers for DOMImplementation, DOMDocumentType, DOMDocument (minimal)
PHP-in-PHP	Tree nodes in ext/dom/ + VM object handlers	Do not grow runtime/*.c; thin libxml ABI only if unavoidable
libxml	host libxml2 for v1 acceptable	Pairs with #6058 error buffer migration
Tests	test/compliance/cases/dom/implementation_create_document.phpt
JIT/AOT	VM-first v1

v1: createDocument, createDocumentType, hasFeature('XML','2.0'). Defer: XPath (#6066), import bridges (#6057).

Done when

• Repro emits well-formed XML matching Zend shape (DOCTYPE + root element)
• hasFeature returns expected booleans for XML/HTML features
• class_exists('DOMImplementation') true; registered as internal class
• ./script/ci-fast.sh --filter DOMImplementation green
• PR notes lines not added to lib/AOT/runtime/*.c (PHP path only)

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter DOMImplementation'

Links

• DOM tree: Stdlib: ext/dom — DOMDocument/DOMElement XML tree API (ext/dom parity) #3326, Stdlib: DOMXPath — XPath queries on DOMDocument missing (ext/dom/xpath.c) #6066
• libxml errors: php-in-php: libxml error buffer — libxml_use_internal_errors/get_errors/clear_errors without host libxml (ext/libxml) #6058
• North star: Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: PHP Runtime → PHP — starting this run (#6140: ext/dom DOMImplementation createDocument/createDocumentType without host DOM).

[PurHur]

Merged via #7742.

PHP-in-PHP: New ext/dom/ module — VmDom + DomRegistry own document/doctype state; DOMImplementation::{createDocumentType,createDocument,hasFeature} and DOMDocument::saveXML on VM without host \\DOM*.

C runtime: No new runtime/*.c symbols (Linker still only phpc_progress.c).

Verification (green):
```bash
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
vendor/bin/phpunit test/unit/DomModuleTest.php test/compliance/DOMImplementationVMTest.php
php bin/vm.php test/repro-maintainer/dom_implementation_6140.php
'
```