Destroy xpath callbacks at the time when the reconstruction happens

ext/dom/tests/DOMXPath_constructor_registered_functions.phpt

@@ -0,0 +1,53 @@
+--TEST--
+DOMXPath: Calling __construct() again when functions were already registered
+--EXTENSIONS--
+dom
+--SKIPIF--
+<?php
+if (!class_exists('DOMXPath')) die('skip no xpath support');
+?>
+--FILE--
+<?php
+
+$dom = new DOMDocument;
+$dom->loadXML('<root/>');
+
+class Test {
+    public function __destruct() {
+        echo "destruct\n";
+    }
+
+    public function test() {
+        echo "test\n";
+    }
+}
+
+echo "=== First run ===\n";
+
+$xpath = new DOMXPath($dom);
+$xpath->registerNamespace('foo', 'urn:foo');
+$xpath->registerPhpFunctionNS('urn:foo', 'test', [new Test, 'test']);
+
+echo "=== Reconstruct ===\n";
+
+$xpath->__construct($dom, true);
+
+echo "=== Second run ===\n";
+
+$xpath->registerNamespace('foo', 'urn:foo');
+$xpath->query('//*[foo:test()]');
+$xpath->registerPhpFunctionNS('urn:foo', 'test', [new Test, 'test']);
+$xpath->query('//*[foo:test()]');
+
+?>
+--EXPECTF--
+=== First run ===
+=== Reconstruct ===
+destruct
+=== Second run ===
+
+Warning: DOMXPath::query(): xmlXPathCompOpEval: function test not found in %s on line %d
+
+Warning: DOMXPath::query(): Unregistered function in %s on line %d
+test
+destruct

ext/dom/xpath.c

@@ -137,6 +137,8 @@ PHP_METHOD(DOMXPath, __construct)
 	if (oldctx != NULL) {
 		php_libxml_decrement_doc_ref((php_libxml_node_object *) &intern->dom);
 		xmlXPathFreeContext(oldctx);
+		php_dom_xpath_callbacks_dtor(&intern->xpath_callbacks);
+		php_dom_xpath_callbacks_ctor(&intern->xpath_callbacks);
 	}
 
 	xmlXPathRegisterFuncNS (ctx, (const xmlChar *) "functionString",

ext/dom/xpath_callbacks.c

@@ -46,6 +46,9 @@ PHP_DOM_EXPORT void php_dom_xpath_callback_ns_dtor(php_dom_xpath_callback_ns *ns
 
 PHP_DOM_EXPORT void php_dom_xpath_callbacks_ctor(php_dom_xpath_callbacks *registry)
 {
+	registry->php_ns = NULL;
+	registry->namespaces = NULL;
+	registry->node_list = NULL;
 }
 
 PHP_DOM_EXPORT void php_dom_xpath_callbacks_clean_node_list(php_dom_xpath_callbacks *registry)