Search engine placement is sort of my specialty, but I hadn't replied to this post because I didn't know how SE robots reacted to PHP. I do know it's rare to see a message board get a good SE result for a particular subject -- it tends to be a well-written index page leading to the board which gets the attention (put the word "hysterectomy" in Google and you'll see that
http://www.hystersisters.com/index gets the good result, even though it's essentially just a doorway to their popular board). Periodically you'll see boards, blogs, or journals getting good placement, but then the SE changes the algorithm and they vanish again. I will say this -- if an index page leading to your message board isn't getting good placement for the search term you want, it will be hard to get your message board to show up in the results independently.
The other comment Josh made is correct -- links to your site are more valuable than the actual content on your site. If you have a site about, oh, "cows", and it's called the "Bovine Chronicles", you're better off getting 3 people linking to you with the word "cows" than having 10 people linking to you using "Bovine Chronicles". That's assuming you want people to find your site if they enter the word "cows" in a search engine.
An excellent resource for this type of stuff is
www.WebmasterWorld.com . They're a tough crowd but very knowledgeable.
