recursion question

I'm trying to write my first recursive function but I'm not doing too well. I have a mysql database with the fields of topic_id, topic_name, and parent_topic_id. If I have a topic_id with a parent_topic_if of 5, I want the function to get the topic_name and parent_topic_id for 5, and again and again until it reaches a parent_topic_id of 0, which would be my top level. As it goes, it would store these values in an array which I can run through later to build a path from the top to whatever topic_id i started out at. What I can't figure is how to set up the recursive function to do so. I have no problem with the database stuff, but I need help with the function stuff. Any ideas or suggestions are greatly appreciated. Robert Cissell