[Misiur]

Your IsVehicleDriver needs fix - it should return player id:
I renamed it for clarity

pawn Код:

forward GetVehicleDriverId(vehicleid);
(...)
public GetVehicleDriverId(vehicleid)
{
    for(new pid=0;pid<=MAX_PLAYERS;pid++)
    {
        if(IsPlayerInVehicle(pid, vehicleid) && GetPlayerState(pid) == PLAYER_STATE_DRIVER) return pid;
    }
    return INVALID_PLAYER_ID;
}

now for the main part of code:

pawn Код:

public OnPlayerExitVehicle(playerid, vehicleid)
{
    if(IsATaxi(vehicleid))
    {
        new s[180], taxiDriverId = GetVehicleDriverId(vehicleid);
        //Do not trigger action for driver
        if(playerid == taxiDriverId) return 1;
        
        GivePlayerMoney(taxiDriverId , PlayerFare[taxiDriverId]);
        GivePlayerMoney(playerid, -PlayerFare[taxiDriverId]);
        format(s,sizeof(s),"You've exited the taxi and paid $%d.", PlayerFare[taxiDriverId]);
        SendClientMessage(playerid, COLOR_LIGHTBLUE, s);
        format(s,sizeof(s),"%s has exited your taxi. You've received $%d.", GetName(playerid), PlayerFare[taxiDriverId]);
        SendClientMessage(taxiDriverId, COLOR_LIGHTBLUE, s);
    }
    return 1;
}

Try this