Create/update nested array from a single array

I'm trying to create a very specific data structure with simple arrays but have got into some issues that I have troubles solving.

I have an empty array and one that I want to build the empty array from.

$roles = []; 
$role_structure = ['domain', 'role_category', 'role'];

What I want it to do is to build an array structure from that there the last entry of the role_structure is set to true and the rest is the key value.

I've written a recursive function to accomplish this:

static function recursive_append_children($arr, $arr_to_append) {
        $shifted_val = array_shift($arr_to_append);
        if (array_key_exists($shifted_val, $arr)) {
            $arr[$shifted_val] = static::recursive_append_children($arr[$shifted_val], $arr_to_append);
        } else {
            $arr[$shifted_val] = count($arr_to_append) > 0 ? static::recursive_append_children($arr,
                $arr_to_append) : true;
        }
        return $arr;
    }

Which works fine if the first array is empty. But if there already is a defined role_structure in the $roles array I just want it to add the new role to the existing array.

So, for example I can send run the first example and it will give me the following output:

['domain' => ['role_category' => ['role' => true]]]

But if I send in the result array as the first parametar to the function above and with another second parameter array that looks like this ['domain', 'another_role_category', 'another_role'] it will produce the following array:

['domain' => [
    'role_category' => ['role' => true],
    'another_role_category' => [
        'role_category' => ['role' => true],
        'another_role' => true
    ]
]

As you surely understand, I don't want two of the role_category and I want to be able to update the first array without duplicating the values. I hope you understand my issue and I am grateful for all help.

Thanks.