Updated the code example

Author: javiereguiluz

components/property_access.rst

@@ -207,7 +207,7 @@ The ``getValue()`` method can also use the magic ``__get()`` method::
 
         public function __isset($id): bool
         {
-            return array_key_exists($id, $this->children);
+            return isset($this->children[$id]);
         }
     }