I am trying to use SimplePie to pull a group pool flickr feed:

$feed = new SimplePie();
$feed->set_feed_url('http://api.flickr.com/services/feeds/groups_pool.gne?id=25938750@N00&lang=en-us&format=rss_200');
$feed->init();
$feed->handle_content_type(); 

Then I use typical SimplePie php calls to loop through the feed items. However, nothing is returned. The HTML is there, but the feed elements aren't inserted.

When I try to use a flickr feed of tags, like:

$feed->set_feed_url('http://api.flickr.com/services/feeds/photos_public.gne?tags=architecture,building&lang=en-us&format=rss_200');

I get back a list of photos from the public photo feed, but the tags aren't taken into account.

Any ideas? The only thing I can think of is I need an API key, but there is nothing on the flickr website that indicates a key is needed for feed calls. Plus, I can open both types of feeds in my browser and get the feed I am looking for.