Array
(
    [0] => Array
        (
            [a] => 1
            [b] => 2
            [c] => 3
        )

    [1] => Array
        (
            [a] => 4
            [b] => 5
            [c] => Array
                (
                    [d] => 6.1
                    [e] => 6.2
                )

        )

    [2] => Array
        (
            [a] => 7
            [b] => 8
            [c] => 9
        )

)
4
Array
(
    [a] => 4
    [b] => 5
    [c] => Array
        (
            [d] => 6.1
            [e] => 6.2
        )

)

6.1