/**
* Turns on caching and checks if there is a recent version of this feed in the cache.
* If there is, an HTTP redirect header is sent.
* To effectively use caching, you should create the FeedCreator object and call this method
* before anything else, especially before you do the time consuming task to build the feed
* (web fetching, for example).
*
* @param string $format format the feed should comply to. Valid values are:
* "PIE0.1" (deprecated), "mbox", "RSS0.91", "RSS1.0", "RSS2.0", "OPML", "ATOM0.3".
* @param string $filename optional the filename where a recent version of the feed is saved. If not specified, the filename is $_SERVER["PHP_SELF"] with the extension changed to .xml (see _generateFilename()).
* @param int $timeout optional the timeout in seconds before a cached version is refreshed (defaults to 3600 = 1 hour)
*/
function useCached($format = "RSS0.91", $filename = "", $timeout = 3600)
{
$this->_setFormat($format);
$this->_feed->useCached($filename, $timeout);
}
