ciao...

quando faccio eseguire il comando :

<?php
$username = $_GET ['login'];
setcookie("dati[3]","$username") ;
?>

mi appare questo errore :

Warning: Cannot modify header information - headers already sent by (output started at c:\programmi\apache group\apache\htdocs\magazzinocook.php:9) in c:\programmi\apache group\apache\htdocs\magazzinocook.php on line 13


come mai??

grazie