[Konstantinos]

You can also use functions from foreach/y_iterate if you already use it since there are Iter_Next and Iter_Prev in it.

PHP код:

GetNextPlayerID(id)
{
    new
        next_id;
    if ((next_id = Iter_Next(Player, id)) != MAX_PLAYERS) return next_id;
    return ((next_id = Iter_First(Player)) == id) ? INVALID_PLAYER_ID : next_id;
}
GetPreviousPlayerID(id)
{
    new
        previous_id;
    if ((previous_id = Iter_Prev(Player, id)) != MAX_PLAYERS) return previous_id;
    return ((previous_id = Iter_Last(Player)) == id) ? INVALID_PLAYER_ID : previous_id;
}