multidimensional array sort

I have a multidimensional array that's built as follows (it's pretty much a directory tree): Array ( [Dir1] => Array (

     [User1] => Array (
         [0] => File1
         [1] => File2
     )
     [User2] => Array {
         [0] => File1
         [1] => File2
         [2] => File3
     }

) [Dir2] => Array (

     [User1] => Array (
         [0] => File1
         [1] => File2
         [2] => File3
         [3] => File4
     )
     [User2] => Array {
         [0] => File1
     }

) ) I need to do a sort on the whole thing in such a way that:

      a) all the Dir#'s are in ascending order, and
      b) all the User#'s are in ascending order with each Dir#, and
      b) all the File#'s are also in ascending order within each User#

I don't suppose there's an easy way to do this, other than doing it in several steps, is there? Is there even a way to JUST sort the Dir#'s (and the rest gets done at a later stage in the script)? -- A