gistfile1.php

  <?php
  
  class RouterThing {
      /* ... */
  
      function fireController($controllerInstance, $action) {
          /* ... setup ... */
          
          $before = get_object_vars($controllerInstance);
          $result = $controllerInstance->$action();
          $scoped = array_diff($before, get_object_vars($controllerInstance));
          
          $this->handleResponse($result, $scoped); // or whatever
      }
      
      /* ... */
  }