Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [foo] => Array
        (
            [0] => 4
            [1] => 5
            [2] => 6
        )

)
Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [foo] => Array
        (
            [1] => 5
            [2] => 6
        )

)