well i wanted to change the url of the forum..

i can get the url like this using php and mysql:
http://www.xyz.com/forum/topic.php?id=2& title=this-is-a-topic&page=11

i wanna change the above url to look like this:
http://www.xyz.com/forum/2/this-is-a-topic/11/

how can i achieve this??