[Larceny]

Just remove it:

pawn Код:

if(i != playerid)
{

}

pawn Код:

if(strcmp(cmdtext, "/lock", true)==0)
{
    if(IsPlayerInAnyVehicle(playerid))
    {
        new State = GetPlayerState(playerid);
        new Float:X, Float:Y, Float:Z;
        // ^
        if(State!=PLAYER_STATE_DRIVER)
        {
            SendClientMessage(playerid,COLOR_GREY,"You can only lock the doors as the driver.");
            return 1;
        }
        new i;
        for(i=0;i<MAX_PLAYERS;i++)
        {
            SetVehicleParamsForPlayer(GetPlayerVehicleID(playerid),i, 0, 1);
        }
        SendClientMessage(playerid, COLOR_GREY, "Vehicle locked!");
        GetPlayerPos(playerid,X,Y,Z);
        PlayerPlaySound(playerid,1056,X,Y,Z);
    }
    else
    {
        SendClientMessage(playerid, COLOR_GREY, "You're not in a vehicle!");
    }
    return 1;
}

Now it will lock for everybody, also who used command.