I'm pretty green when it comes to PHP, but I do know that newer versions of MS IE can display word documents in the browser if you have office installed on your computer, but all of the pages that I have seen do this end in a .doc extension.
I'm guessing you would have to have you web server parse all .doc files through PHP. You could then write a script which would select the correct entry from the mysql database and send it to the browser, using a script that ends in a .doc extension instead of .php. That way, the browser would think that it's being passed a word document.