Filtering an RSS feed based on keyword?

My client’s site has a bulletin board (phpbb). In the board there is a forum for sharing/trading sporting tickets.

My client wants me to come up with a way to display posts from that forum in the users’ personal area of the site. Kind of a “my favorite posts” section. He wants the user to be able to filter these posts based on phrases like “Tampa Bay Bucs” or “New York Rangers” etc. so only posts with those phrases are displayed.

The forum generates an Atom feed. I can get the url of the feed and use SimpleXML to display the feed, but how do I create the ability to filter it per individual user?

Essentially my clients want me to built capability into his site.

I think you just need functions that allow users to specify their keywords and then find the keywords in feeds content and display it. I don’t think it’s hard by using PHP.

Yes, I’m not quite sure how to go about it.

Say I have a list of user-supplies phrases (A) that are pulled from a database like this:

  1. Tampa Bay Bucs
  2. St. Louis Cardinals
  3. New York Rangers

And a master phrase to check them against (B) like this:

“Tickets for sale - Bucs vs. Cardinals”

How do I write a function that will determine if any phrase within A is within B?