code: public function remove($item)
      {
          if (is_object($item)) {
              unset($this->_items[$item->primaryKey]);
          } else {
              unset($this->_items[$item]);
          }
      }
docs: Removes a item.
  If `$removeFromBrowser` is true, the item will be removed from the browser.
  In this case, a item with outdated expiry will be added to the collection.
  
  @param string $item the item object or the name of the item to be removed.
  
  @throws InvalidCallException if the item collection is read only