code: public function getFrameFocus()
      {
          if ($this->focus === false) {
              return array();
          }
  
          return array_merge(
                  array($this->getPublicNameFromIndex($this->focus)),
                  $this->frames[$this->focus]->getFrameFocus());
      }
docs: Accessor for current frame focus.
  Will be false if no frame has focus. Will have the nested frame focus if any.
  
  @return array     Labels or indexes of nested frames.