Reuse namespaces from doc->oldNs if possible in dom_get_ns()

Author: nielsdos

ext/dom/php_dom.c

@@ -1518,20 +1518,33 @@ NAMESPACE_ERR: Raised if
 xmlNsPtr dom_get_ns(xmlNodePtr nodep, char *uri, int *errorcode, char *prefix) {
 	xmlNsPtr nsptr = NULL;
 
-	*errorcode = 0;
-
 	if (! ((prefix && !strcmp (prefix, "xml") && strcmp(uri, (char *)XML_XML_NAMESPACE)) ||
 		   (prefix && !strcmp (prefix, "xmlns") && strcmp(uri, (char *)DOM_XMLNS_NAMESPACE)) ||
 		   (prefix && !strcmp(uri, (char *)DOM_XMLNS_NAMESPACE) && strcmp (prefix, "xmlns")))) {
+		/* Reuse the old namespaces from doc->oldNs if possible, before creating a new one */
+		xmlDocPtr doc = nodep->doc;
+		if (doc && doc->oldNs != NULL) {
+			xmlNsPtr cur = doc->oldNs;
+			do {
+				if (xmlStrEqual(cur->prefix, (xmlChar *)prefix) && xmlStrEqual(cur->href, (xmlChar *)uri)) {
+					nsptr = cur;
+					goto out;
+				}
+				cur = cur->next;
+			} while (cur);
+		}
+		/* Couldn't reuse one, create a new one. */
 		nsptr = xmlNewNs(nodep, (xmlChar *)uri, (xmlChar *)prefix);
 	}
 
 	if (nsptr == NULL) {
 		*errorcode = NAMESPACE_ERR;
+		return NULL;
 	}
 
+out:
+	*errorcode = 0;
 	return nsptr;
-
 }
 /* }}} end dom_get_ns */