Description:
------------
---
From manual page: https://php.net/function.array-merge-recursive
---
When first array first element has higher index number than second element, then array_merge_recursive makes duplicate keys. In php 5 was ok, this was tested on 7.0.32 and 7.1.* - same result.

Test script:
---------------
$aray1 = [
    'service' => [
        5 => ['jehfkjfhwk'],
        2 => ['ejfoiwefoweif']
    ],
];
$aray2 = [
    'service' => [
        ['qfwwqfqwf'],
        ['wqfwfqwfqwf1'],
        ['wqfwfqwfqwf2'],
        ['wqfwfqwfqwf3'],
        ['wqfwfqwfqwf4'],
        ['wqfwfqwfqwf5'],
        ['wqfwfqwfqwf6'],
    ],
];

echo '<pre>';
print_r(array_merge_recursive($aaray1, $aaray2));

Expected result:
----------------
Array
(
    [service] => Array
        (
            [5] => Array
                (
                    [0] => jehfkjfhwk
                )

            [2] => Array
                (
                    [0] => ejfoiwefoweif
                )

            [6] => Array
                (
                    [0] => qfwwqfqwf
                )

            [7] => Array
                (
                    [0] => wqfwfqwfqwf1
                )

            [8] => Array
                (
                    [0] => wqfwfqwfqwf2
                )

            [9] => Array
                (
                    [0] => wqfwfqwfqwf3
                )

            [10] => Array
                (
                    [0] => wqfwfqwfqwf4
                )

            [11] => Array
                (
                    [0] => wqfwfqwfqwf5
                )

            [12] => Array
                (
                    [0] => wqfwfqwfqwf6
                )

        )

)

Actual result:
--------------
Array
(
    [service] => Array
        (
            [5] => Array
                (
                    [0] => jehfkjfhwk
                )

            [2] => Array
                (
                    [0] => ejfoiwefoweif
                )

            [2] => Array
                (
                    [0] => qfwwqfqwf
                )

            [3] => Array
                (
                    [0] => wqfwfqwfqwf1
                )

            [4] => Array
                (
                    [0] => wqfwfqwfqwf2
                )

            [5] => Array
                (
                    [0] => wqfwfqwfqwf3
                )

            [6] => Array
                (
                    [0] => wqfwfqwfqwf4
                )

            [7] => Array
                (
                    [0] => wqfwfqwfqwf5
                )

            [8] => Array
                (
                    [0] => wqfwfqwfqwf6
                )

        )

)