simplexml: filter addChild() result by the created element's namespace

addChild() built the returned SimpleXMLElement with the prefix the caller
passed in, not the one the new node ended up in, so a child added through
that object was filtered against the wrong namespace and was invisible by
property name. Take the prefix from newnode->ns instead. The filter keys
on the prefix rather than the href because node_as_zval() installs no
filter at all for a prefixless namespace, and switching to href would
start filtering the default-namespace case that today has none.

Closes GH-23599

Author: iliaal

NEWS

@@ -114,6 +114,9 @@ PHP                                                                        NEWS
 - SimpleXML:
   . Fixed writing to a dimension of the object returned by attributes() not
     creating the attribute. (Ilia Alshanetsky)
+  . Fixed child elements of the element returned by
+    SimpleXMLElement::addChild() not being accessible by property name when
+    namespaces are involved. (Ilia Alshanetsky)
 
 - Zip:
   . Fixed bug GH-23276 (ZipArchive subclass storing its own stream cannot be

ext/simplexml/simplexml.c

@@ -1727,7 +1727,8 @@ PHP_METHOD(SimpleXMLElement, addChild)
 		}
 	}
 
-	node_as_zval_str(sxe, newnode, return_value, SXE_ITER_NONE, localname, prefix, 0);
+	node_as_zval_str(sxe, newnode, return_value, SXE_ITER_NONE, localname,
+		newnode->ns ? newnode->ns->prefix : NULL, 1);
 
 	xmlFree(localname);
 	if (prefix != NULL) {

ext/simplexml/tests/addChild_ns_filter_returned_element.phpt

@@ -0,0 +1,38 @@
+--TEST--
+SimpleXMLElement::addChild() wrong namespace filter on returned element
+--EXTENSIONS--
+simplexml
+--FILE--
+<?php
+$x = new SimpleXMLElement('<r xmlns:a="http://example.com"/>');
+$c = $x->addChild('a:kid', null, 'http://example.com');
+$c->addChild('inner', 'v');
+echo trim($x->asXML()), "\n";
+echo (string) $c->inner, "\n";
+var_dump(isset($c->inner));
+
+$y = new SimpleXMLElement('<r xmlns:a="http://example.com"/>');
+$d = $y->addChild('kid', null, 'http://example.com');
+$d->addChild('inner', 'w');
+echo trim($y->asXML()), "\n";
+echo (string) $d->inner, "\n";
+
+$z = new SimpleXMLElement('<p:r xmlns:p="http://example.com/p"/>');
+$e = $z->addChild('kid');
+$e->addChild('inner', 'z');
+echo trim($z->asXML()), "\n";
+echo (string) $e->inner, "\n";
+var_dump(isset($e->inner));
+?>
+--EXPECT--
+<?xml version="1.0"?>
+<r xmlns:a="http://example.com"><a:kid><a:inner>v</a:inner></a:kid></r>
+v
+bool(true)
+<?xml version="1.0"?>
+<r xmlns:a="http://example.com"><a:kid><a:inner>w</a:inner></a:kid></r>
+w
+<?xml version="1.0"?>
+<p:r xmlns:p="http://example.com/p"><p:kid><p:inner>z</p:inner></p:kid></p:r>
+z
+bool(true)