From 22a113b99c883753762bb637eb7a2a50dca67b10 Mon Sep 17 00:00:00 2001
From: Niels Dossche <7771979+nielsdos@users.noreply.github.com>
Date: Sat, 4 May 2024 13:59:43 +0200
Subject: [PATCH] Try to use an interned local name in createElementNS (#14127)

---
 ext/dom/document.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/ext/dom/document.c b/ext/dom/document.c
index 5706c3d959f..9609fce4ffb 100644
--- a/ext/dom/document.c
+++ b/ext/dom/document.c
@@ -912,7 +912,17 @@ PHP_METHOD(DOM_Document, createElementNS)
 	if (errorcode == 0) {
 		php_dom_libxml_ns_mapper *ns_mapper = php_dom_get_ns_mapper(intern);
 		xmlNsPtr ns = php_dom_libxml_ns_mapper_get_ns_raw_prefix_string(ns_mapper, prefix, xmlStrlen(prefix), uri);
-		xmlNodePtr nodep = xmlNewDocNodeEatName(docp, ns, localname, NULL);
+
+		/* Try to create the node with the local name interned. */
+		const xmlChar *interned_localname = xmlDictLookup(docp->dict, localname, -1);
+		xmlNodePtr nodep;
+		if (interned_localname == NULL) {
+			nodep = xmlNewDocNodeEatName(docp, ns, localname, NULL);
+		} else {
+			xmlFree(localname);
+			nodep = xmlNewDocNodeEatName(docp, ns, BAD_CAST interned_localname, NULL);
+		}
+
 		if (UNEXPECTED(nodep == NULL)) {
 			php_dom_throw_error(INVALID_STATE_ERR, /* strict */ true);
 		} else {