Regression: DOMElement::appendChild(DOMDocument) TypeError — Zend DOMException Hierarchy Request Error (ext/dom/node.c) #22698

Category

stdlib · php-src-strict · DOM tree mutation (pillar 4)

Problem

DOMDocument is a DOMNode subclass. Appending the document itself as a child of an element must raise DOMException with Zend message Hierarchy Request Error and code 3 (DOM_HIERARCHY_REQUEST_ERR). The VM rejects the argument in the typed parameter check with TypeError (expects argument #1 to be of type DOMNode, DOMDocument given) before hierarchy validation runs — despite instanceof DOMNode being true on the same object.

Sibling paths differ: insertBefore($doc, null) reaches a DOMException but with wrong message casing / code 0 (see related #22658/#22694 code-plumbing). replaceChild($doc, $child) and appendChild($ancestor) already emit code 3 correctly.

Probed 2026-07-23 on master VM vs host Zend 8.2.32.

php-src reference

• php/php-src ext/dom/node.c — dom_node_append_child / hierarchy checks; DOMDocument is a valid DOMNode* then rejected as hierarchy
• php/php-src ext/dom/php_dom.c — dom_get_domexception / HIERARCHY_REQUEST_ERR

PHP implementation target

• ext/dom/VmDom.php (appendChild / arg type check) — accept DOMDocument as DOMNode for the parameter, then throw DOMException('Hierarchy Request Error', DomExceptionConstants::HIERARCHY_REQUEST_ERR) like replaceChild already does
• PHP-in-PHP only; no new runtime/*.c logic

Repro

./script/docker-exec.sh -- bash -lc 'php bin/vm.php -r '"'"'
$d = new DOMDocument();
$e = $d->createElement("a");
$d->appendChild($e);
echo "instanceof DOMNode=", $d instanceof DOMNode ? "yes" : "no", "\n";
try {
  $e->appendChild($d);
  echo "OK\n";
} catch (Throwable $ex) {
  echo get_class($ex), ": ", $ex->getMessage(), "\n";
  if ($ex instanceof DOMException) echo "code=", $ex->getCode(), "\n";
}
echo "DOM_HIERARCHY_REQUEST_ERR=", DOM_HIERARCHY_REQUEST_ERR, "\n";
'"'"''

Done when

• $e->appendChild($d) throws DOMException with message Hierarchy Request Error and code 3 (not TypeError)
• Compliance .phpt under test/compliance/cases/stdlib/ (or dom/)
• php-src-strict; no php-compiler-strict shortcut
• Prefer shared DOMException helper with Regression: DOMException WRONG_DOCUMENT_ERR code is 0 — Zend code 4 (ext/dom/php_dom.c) #22658/Regression: DOMException NOT_FOUND_ERR code is 0 — Zend code 8 (ext/dom/php_dom.c) #22694 rather than one-off codes