Cover more paths in dom_xpath_ext_function_php() with tests

Also removes an incorrect comment: we *do* need the special namespace
node handling code, otherwise we'd segfault.

ext/dom/tests/DOMXPath_evaluate_namespace_node_set.phpt

@@ -0,0 +1,33 @@
+--TEST--
+DOMXPath::evaluate() with PHP function passing a namespace node-set
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container>
+    <p>hi</p>
+</container>
+XML);
+
+$xpath = new DOMXPath($dom);
+
+function node_test($nodes) {
+    echo "nodes count: ", count($nodes), "\n";
+    return array_sum(array_map(fn ($node) => strlen($node->nodeName), $nodes));
+}
+
+$xpath->registerNamespace("php", "http://php.net/xpath");
+$xpath->registerPhpFunctions(['node_test']);
+var_dump($xpath->evaluate('number(php:function("node_test", //namespace::*))'));
+var_dump($xpath->evaluate('boolean(php:function("node_test", //namespace::*))'));
+
+?>
+--EXPECT--
+nodes count: 2
+float(18)
+nodes count: 2
+bool(true)

ext/dom/tests/DOMXPath_evaluate_node_set_to_string.phpt

@@ -0,0 +1,26 @@
+--TEST--
+DOMXPath::evaluate() with PHP function passing node-set returning a string
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container>
+    <p>hi</p>
+</container>
+XML);
+
+$xpath = new DOMXPath($dom);
+
+$xpath->registerNamespace("php", "http://php.net/xpath");
+$xpath->registerPhpFunctions(['strrev']);
+var_dump($xpath->evaluate('php:functionString("strrev", //p)'));
+var_dump($xpath->evaluate('php:functionString("strrev", //namespace::*)'));
+
+?>
+--EXPECT--
+string(2) "ih"
+string(36) "ecapseman/8991/LMX/gro.3w.www//:ptth"

ext/dom/xpath.c

@@ -100,7 +100,6 @@ static void dom_xpath_ext_function_php(xmlXPathParserContextPtr ctxt, int nargs,
 						for (j = 0; j < obj->nodesetval->nodeNr; j++) {
 							xmlNodePtr node = obj->nodesetval->nodeTab[j];
 							zval child;
-							/* not sure, if we need this... it's copied from xpath.c */
 							if (node->type == XML_NAMESPACE_DECL) {
 								xmlNodePtr nsparent = node->_private;
 								xmlNsPtr original = (xmlNsPtr) node;