[Tr1viUm]

IsAnyTrailerAttachedToVehicle

Returns 1 when a trailer is attacked to the vehicle, 0 otherwise.

Code:

IsAnyTrailerAttachedToVehicle(vehicleid)
{
	new trailerid = GetVehicleTrailer(vehicleid);
	new modelid = GetVehicleModel(trailerid);
	if(modelid == 435 || modelid == 450 || modelid == 591 || modelid == 606 || modelid == 607 ||
	modelid == 610 || modelid == 569 || modelid == 590 || modelid == 584 || modelid == 570 ||
    modelid == 608 || modelid == 611) return true;	

	return false;
}

GetPlayersInVehicle
This function simpely returns the amount players in a vehicle. (0 if it is empty)

Code:

GetPlayersInVehicle(vehicleid)
{
  new amount = 0;
  for(new i = 0; i < GetMaxPlayers(); i++)
  {
    if(!IsPlayerConnected(i) || !IsPlayerInVehicle(i,vehicleid))
      continue;
    amount++;
  }
  return amount;
}