Fix GH-16317: SimpleXML does not allow __debugInfo() overrides to work

If only we did not have the pseudo-key "@attributes", we could've just
removed the custom get_debug_info implementation and this would work out
of the box. Anyway, we just have to manually check for an override now.

Author: ndossche

ext/simplexml/simplexml.c

@@ -1225,8 +1225,14 @@ static HashTable *sxe_get_properties(zend_object *object) /* {{{ */
 }
 /* }}} */
 
+/* This custom handler exists because the var_dump adds a pseudo "@attributes" key. */
 static HashTable * sxe_get_debug_info(zend_object *object, int *is_temp) /* {{{ */
 {
+	/* As we have a custom implementation, we must manually check for overrides. */
+	if (object->ce->__debugInfo) {
+		return zend_std_get_debug_info(object, is_temp);
+	}
+
 	*is_temp = 1;
 	return sxe_get_prop_hash(object, 1);
 }

ext/simplexml/tests/gh16317.phpt

@@ -0,0 +1,22 @@
+--TEST--
+GH-16317 (SimpleXML does not allow __debugInfo() overrides to work)
+--FILE--
+<?php
+
+class MySXE extends SimpleXMLElement {
+    public function __debugInfo(): array {
+        echo "invoked\n";
+        return ['x' => 1];
+    }
+}
+
+$sxe = simplexml_load_string('<root><a/></root>', MySXE::class);
+var_dump($sxe);
+
+?>
+--EXPECT--
+invoked
+object(MySXE)#1 (1) {
+  ["x"]=>
+  int(1)
+}