code: public static function findParentsById($intId)
  	{
  		$arrModels = array();
  
  		while ($intId > 0 && ($objPage = static::findByPk($intId)) !== null)
  		{
  			$intId = $objPage->pid;
  			$arrModels[] = $objPage;
  		}
  
  		if (empty($arrModels))
  		{
  			return null;
  		}
  
  		return static::createCollection($arrModels, 'tl_page');
  	}
docs: Find the parent pages of a page
  
  @param integer $intId The page's ID
  
  @return Collection|PageModel[]|PageModel|null A collection of models or null if there are no parent pages