In case you aren't on the Flickr API mailing list and you've been itching to use the new collections feature in your API application, Eric Costello responded to someone asking when "collections" will be available in the API:
Probably months. Could be sooner, but we have a whole lot of higher priority things going on right now, and before we release the APIs for collections there are some changes we need to make to how collections work (we're changing them to handle mixed content). We definitely know there is developer interest in the collection APIs, so we'll get to it as soon as possible. Thanks for your patience
I will be trying to update phpFlickr as soon as those API calls are available.