/**
* Autodiscovers a feed url from a given url, to be used by the formslibs
* filter function
*
* Uses simplepie with autodiscovery set to maximum level to try and find
* a feed to subscribe to.
* See: http://simplepie.org/wiki/reference/simplepie/set_autodiscovery_level
*
* @param string URL to autodiscover a url
* @return string URL of feed or original url if none found
*/
public static function autodiscover_feed_url($url)
{
$rss = new moodle_simplepie();
$rss->set_feed_url($url);
$rss->set_autodiscovery_level(SIMPLEPIE_LOCATOR_ALL);
// When autodiscovering an RSS feed, simplepie will try lots of
// rss links on a page, so set the timeout high
$rss->set_timeout(20);
$rss->init();
if ($rss->error()) {
return $url;
}
return $rss->subscribe_url();
}