Someone

public OnPlayerEnterVehicle(playerid, vehicleid, ispassenger)
{
	printf("OnPlayerEnterVehicle(%d, %d, %d)", playerid, vehicleid, ispassenger);
 	if (vehicleid == 0 || vehicleid == 1 || vehicleid == 2 || vehicleid == 3 || vehicleid == 4){
	    if (gTeam[playerid] == TEAM_TAXI){
	    	SendClientMessage(playerid, COLOR_YELLOW, ">> You have entered a taxi as the taxi driver.");
	    	if (gTaxiFee[playerid] == 0){
	    		SendClientMessage(playerid, COLOR_YELLOW, ">> Please set a taxi fee by typing /setfee <amount>");
			}
			else {
			    new str[STR_LEN] = "";
			    format(str, STR_LEN, ">> Your fee is currently %d", gTaxiFee[playerid]);
			    SendClientMessage(playerid, COLOR_YELLOW, str);
   			}
	    	SendClientMessage(playerid, COLOR_YELLOW, ">> Go make some money!");
	    	gIsInTaxi[playerid] == 1;
	    }
	    else {
	        if(GetPlayerState(playerid) == PLAYER_STATE_PASSENGER){
	            new DriverID;
	            DriverID = GetVehicleDriverID(vehicleid, playerid)
	            //DriverID now holds the ID of the driver of the vehicle.
	            if(!DriverID == -1)
	            {
	            //There is a driver in this taxi
	            	//
	            	//Do funky code
	            	//
	            }else{
	            //There is no driver in this taxi
	            }
	            //gPayFee[playerid] = gTaxiFee[];
	        }
	        else {
	    		SendClientMessage(playerid, COLOR_YELLOW, ">> You are not a taxi driver. No profit will be made.");
	        }
	    }
  	}
	return 1;
}

public GetVehicleDriverID(vehicleid, passengerplayerid)
{
	new Result = -1;
	for(new i=0; i<MAX_PLAYERS;i++)
	{
	    //We dont want to scan the passenger player ID..
	    if(!i == passengerplayerid)
	    {
		    //Check if this player is inside the vehicle ID Supplied
		    if(IsPlayerInVehicle(i,vehicleid)) {
				Result = i;
		    }
		}
	}
	
	return Result;
}