Sorting Multidimensional Associative arrays

I'm trying to sort a multidimensional asociative array. The array looks like this: $r[$user]['skill'] $r[$user]['age'] $r[$user]['experience'] is it possible to sort this array in such way that the first key of it (user) is the user with the highest age number and the last user is the one with lowest age number? That is.. an descending sorting of users by their age. If it were a mysql database. what i want is something like "SELECT user FROM table ORDER BY skill DESC" but since it's an array and not a sql ... I have no clue :) You may ask.. why dont I have that info at an sql so I could make a simple query... well, I might have some reasons for not doing it. but that's not the point. so please if anyone knows how to sort the array.. any examples would be really helpfully :)) Thanks in advance Alex.