Merge branch '5.4' into 6.4

* 5.4:
  implement __isset() together with __get()

components/property_access.rst

@@ -258,16 +258,21 @@ The ``getValue()`` method can also use the magic ``__get()`` method::
         {
             return $this->children[$id];
         }
+
+        public function __isset($id): bool
+        {
+            return true;
+        }
     }
 
     $person = new Person();
 
     var_dump($propertyAccessor->getValue($person, 'Wouter')); // [...]
 
-.. note::
+.. caution::
 
-    The ``__get()`` method support is enabled by default.
-    See `Enable other Features`_ if you want to disable it.
+    When implementing the magic ``__get()`` method, you also need to implement
+    ``__isset()``.
 
 .. _components-property-access-magic-call: