[[DOG]irinel1996]

Someone suggested this for SA-MP 0.3x, so I tried to make it:

pawn Код:

stock GetVehiclePlayerInSeat(vehicleid, seatid) {
    if (!GetVehicleModel(vehicleid)) return INVALID_VEHICLE_ID;
    new
        total = GetMaxPlayers()
    ;
    for (new x; x < total; x++) {
        if (IsPlayerConnected(x)) {
            if (IsPlayerInAnyVehicle(x) && GetPlayerVehicleSeat(x) == seatid) {
                return x; //Thanks ****** for making me notice this. (player id 0 issue)
                break;
            }
        }
    }
    return INVALID_PLAYER_ID; //Thanks Slice
}

Returns:
x -> player's id who is seated on the seatid.
INVALID_VEHICLE_ID -> the vehicle doesn't exist.
INVALID_PLAYER_ID -> the seatid is empty.

PD: I didn't test it, but I guess it should work.

Best regards!

EDIT: Tested.