[Florin48]

not necessarily, he can create a KeyCar variable [playerid] = -1; when connecting and after trying to make the order.

CMD:givekey(playerid, params[])
{
new id;
sscanf(params,"u",id)) return SendClientMessage(playerid, -1, "/givekey [username/id]");
if(!IsPlayerInVehicle(playerid, /*Your vehicle*/)) return /*Message*/
KeyCar[id] = /*Your vehicle ID*/
...
return 1;
}

it's just a simple exemple, you must to try to make your own commands