Fix get_object_vars() for non-hooked props in hooked prop iter

Very confusingly, the zend_hash_update_ind() variant unwraps indirects, rather
than creating them. Don't use _zend_hash_append_ind() because the property might
already exist.

Fixes GH-16725

Zend/tests/gh16725.phpt

@@ -0,0 +1,27 @@
+--TEST--
+GH-16725: Incorrect access check for non-hooked props in hooked object iterator
+--FILE--
+<?php
+
+class C implements JsonSerializable
+{
+    private string $prop1 { get => 'bar'; }
+
+    public function __construct(
+        private string $prop2,
+    ) {}
+
+    public function jsonSerialize(): mixed {
+        return get_object_vars($this);
+    }
+}
+
+$obj = new C('foo');
+var_dump(get_object_vars($obj));
+echo json_encode($obj);
+
+?>
+--EXPECT--
+array(0) {
+}
+{"prop1":"bar","prop2":"foo"}

Zend/zend_property_hooks.c

@@ -89,7 +89,8 @@ static zend_array *zho_build_properties_ex(zend_object *zobj, bool check_access,
 				if (UNEXPECTED(Z_TYPE_P(OBJ_PROP(zobj, prop_info->offset)) == IS_UNDEF)) {
 					HT_FLAGS(properties) |= HASH_FLAG_HAS_EMPTY_IND;
 				}
-				zend_hash_update_ind(properties, property_name, OBJ_PROP(zobj, prop_info->offset));
+				zval *tmp = zend_hash_lookup(properties, property_name);
+				ZVAL_INDIRECT(tmp, OBJ_PROP(zobj, prop_info->offset));
 			}
 skip_property:
 			if (property_name != prop_info->name) {