[Diti1]

Try this
CMD:b(playerid, params[])
{
new sendername[MAX_PLAYER_NAME], string[56];
GetPlayerName(playerid, sendername, sizeof(sendername));
if(isnull(params)) return SendClientMessage(playerid, 0xFFFFFFF,"Syntax error.Correct usage: /b [text]");
format(string, sizeof(string), "(( %s: %s ))", sendername, params);
SendClientMessageToAll(0xFFFFFFF, string);
return 1;
}