Exception: and needs an array. Where is the mistake?

Question

MongoDB

Good day.
Something incomprehensible is going on ...
The request to the monge looks like this:

Array
(
    [$and] => Array
        (
            [1] => Array
                (
                    [$or] => Array
                        (
                            [0] => Array
                                (
                                    [stateId] => 11
                                )

                        )

                )

        )

)

It gives an error, such as not an array, but what is it then? I put an index to the array to group requests.
exception: and needs an array
Now the most interesting thing, change the key "1" to "0" and everything is OK, no errors.

Array
(
    [$and] => Array
        (
            [0] => Array
                (
                    [$or] => Array
                        (
                            [0] => Array
                                (
                                    [stateId] => 11
                                )

                        )

                )

        )

)

I dug a little and realized that the numbering cannot start with "1", if there is no zero element, an error occurs, such as not an array. Into bullshit...