ok -1- ok 
Array
(
    [a] => apple
    [b] => banana
    [c] => Array
        (
            [0] => x
            [1] => y
            [2] => z
        )

)

ok -2- ok 
Array
(
    [m] => monkey
    [foo] => bar
    [xxx] => Array
        (
            [0] => x
            [1] => y
            [2] => z
        )

)

ok -3- ok 
Array
(
    [m] => apple
    [foo] => rebar
    [x] => Array
        (
            [0] => x
            [1] => y
            [2] => z
        )

)