I've never worked w/ .dbf files, I've never had to because MySQL is so much cooler... 🙂 If you don't have MySQL, get it now, because it's free and practically the standard (especially on this board). There's a whole set of mysql functions in PHP that will save you a lot of work.
In other words, I can't help you with this problem, but if you come to the board with a problem in mysql you are much more liekly to get a quick response...
Good luck!
Jason