bool CALLBACK outRPC(stRakNetHookParams *params) 
{
    if (params->packetId == RPCEnumeration::RPC_EnterVehicle) 
    {
        int16 vehID;
        bool asPassenger;
        char buf[255];

        params->bitStream->ResetReadPointer(); 
        params->bitStream->Read(vehID);
        params->bitStream->Read(asPassenger);
        params->bitStream->ResetReadPointer();

        sprintf(buf, "I enter the car ID: %i", vehID);
        SF->getSAMP()->getPlayers()->pLocalPlayer->Say(buf);
    };
    return true; 
};

SF->getRakNet()->registerRakNetCallback(RakNetScriptHookType::RAKHOOK_TYPE_OUTCOMING_RPC, outRPC); // in mainloop()