<?php

$result = (function(array $values) {
    function _sort(array &$values)
    {
        ksort($values);
        $name = __FUNCTION__;
        foreach (array_keys($values) as $key) {
            if (is_array($values[$key])) {
                $name($values[$key]);
            }
        }
    }
    $result = $values;
    _sort($result);

    return $result;
})([
    'b' => [
        'd' => 1,
        'v' => 0,
        'a' => [
            'x' => 10,
        ],
    ],
    'a' => [
        'v' => 0,
        'a' => [
            'x' => 10,
        ],
    ]
]);
print_r($result);