Array sort

Before sort

Array
(
    [1] => d
    [2] => 3
    [3] => u
    [4] => 9
    [5] => n
    [6] => 3
    [7] => u
    [8] => D
    [9] => Y
)

After sort

Array
(
    [0] => 3
    [1] => 3
    [2] => 9
    [3] => D
    [4] => Y
    [5] => d
    [6] => n
    [7] => u
    [8] => u
)