code: public function free()
      {
          unset($this->tags);
          unset($this->page);
          unset($this->private_content_tags);
          $this->open_forms             = array();
          $this->complete_forms         = array();
          $this->frameset               = false;
          $this->loading_frames         = array();
          $this->frameset_nesting_level = 0;
          $this->left_over_labels       = array();
      }
docs: Frees up any references so as to allow the PHP garbage collection from unset() to work.