To rearrange structure of multi dimensional array

Question

array1:
Array
(
   "Page change" => Array
        (
           Array("parent_id" =>,"access_id" => 1),
           Array("parent_id" =>,"access_id" => 2),
           Array("parent_id" =>2,"access_id" =>3),
           Array("parent_id" =>2,"access_id" =>4),
           Array("parent_id" =>,"access_id" =>5),
           Array("parent_id" =>5,"access_id" =>6),
        )

   "Roles" => Array
        (
            Array("parent_id" =>5,"access_id" =>7),
            Array("parent_id" =>,"access_id" =>8),
        )
)

Array2:
Array
(
    [Page change] => Array
        (
            [0] => Array
                (
                    [parent_id] => 
                    [access_id] => 1
                )

            [1] => Array
                (
                    [parent_id] => 
                    [access_id] => 2
                    [sub]=>array(                        
                        [0]=>Array
                            (
                                [parent_id] => 2
                                [access_id] => 3
                            )
                        [1] => Array
                            (
                                [parent_id] => 2
                                [access_id] => 4
                            )
                    )
                )           

            [2] => Array
                (
                    [parent_id] => 
                    [access_id] => 5
                    [sub]=>array(
                        [0] => Array
                        (
                            [parent_id] => 5
                            [access_id] => 6
                        )

                    )
                )           

        )

    [Roles] => Array
        (
            [0] => Array
                (
                    [parent_id] => 
                    [access_id] => 7
                )

            [1] => Array
                (
                    [parent_id] => 
                    [access_id] => 8
                )

        )
)

I am struggling to change the structure of an array.My result array is like structure array one in my code. I need to change that like array two using parent_id and access_id in first array.How can i possibly rearrange this multi-dimensional array

If need add "sub" key in every inner arrays.

Thanks for the help in advance