/**
* Returns the number of seconds after the time specified in the response's Date
* header when the response should no longer be considered fresh.
*
* First, it checks for a s-maxage directive, then a max-age directive, and then it falls
* back on an expires header. It returns null when no maximum age can be established.
*
* @return int|null Number of seconds
*
* @api
*/
public function getMaxAge()
{
return parent::getMaxAge();
}