This tool is now named Tubes and is hosted on Bitbucket.
As I wrote a few months ago, Yahoo Pipes is a nice tool. Nonetheless, it has a few shortcomings which annoyed me because I could neither fix nor work around them. Therefore, I decided to write my own mashup tool. For the impatient, you can download the file right now before reading anything else.
Since SimplePie seems to be the feed aggregation library of choice for many projects, I decided to go with it. I ran into a few minor issues, but nothing I couldn’t handle easily. The code I wrote is based on the multifeeds.php demo file and SimplePie 1.1.3, because in 1.2 it didn’t work (the multifeeds demo, that is — by extension I suppose this file won’t either). It’s a little rough around the edges, and SimplePie is clearly meant for HTML output rather than XML (although its HTML isn’t quite decent either, even if the input feed is), so I decided to fix the whole thing up with Tidy, which takes care of low quality input material as well. Hopefully that makes this whole thing more robust than it would otherwise be. The code is based around bringing various Opera feeds I read together in one big feed, but this can very easily be changed.
So now that I’ve got the basics of output into a feed taken care of, I can easily duplicate other functionality of Yahoo Pipes if I want. Much better.