l'istruzione

setcookie("codUO",$codUO);

mi da l'errore

Notice: Undefined variable: codUO in c:\inetpub\wwwroot\html\uo\oncop\pwd_in.php on line 13

Warning: Cannot modify header information - headers already sent by (output started at c:\inetpub\wwwroot\html\uo\oncop\pwd_in.php:13) in c:\inetpub\wwwroot\html\uo\oncop\pwd_in.php on line 13

come lo risolvo? (register_globals ce l'ho impostato a on)
ciao