[Rzzr]

pawn Код:

public OnPlayerText(playerid, text[])
{
    new string[128];
    format(string,sizeof(string),"(%d) %s",playerid,text);
    SendPlayerMessageToAll(playerid, string);
    return 0;
}

That is the easiest way.
It will show like this:
[ST]DutchBas: (0) Hello I said something