private function arrayMergeDeep(array $array1, array $array2): array
    {
        $result = [];
        foreach (\func_get_args() as $array) {
            foreach ($array as $key => $value) {
                // Renumber integer keys as array_merge_recursive() does. Note that PHP
                // automatically converts array keys that are integer strings (e.g., '1')
                // to integers.
                if (\is_int($key)) {
                    $result[] = $value;
                } elseif (isset($result[$key]) && \is_array($result[$key]) && \is_array($value)) {
                    // Recurse when both values are arrays.
                    $result[$key] = $this->arrayMergeDeep($result[$key], $value);
                } else {
                    // Otherwise, use the latter value, overriding any previous value.
                    $result[$key] = $value;
                }
            }
        }

        return $result;
    }