[DaRk_RaiN]

Code fixed above.
Also:
!= means is he is NOT a driver check
When you should have used ==

pawn Код:

public OnPlayerEnterVehicle(playerid, vehicleid, ispassenger)
{
   if(GetPlayerState(playerid) == PLAYER_STATE_DRIVER )
{
   SendClientMessage(playerid, COLOR_YELLOW, "You have entered a vehicle ((TIP: Type /e to start it.))");
}
   return 1;
}