headers already sent

[amnesiac]

ciao ragazzi! questo script mi da errore su:

header("Location: promemo.php"); 

mi dice:
Warning: Cannot modify header information - headers already sent by (output started at C:\Programmi\Apache Software Foundation\Apache2.2\htdocs\ecom2\ins_dominio.php: 3) in C:\Programmi\Apache Software Foundation\Apache2.2\htdocs\ecom2\ins_dominio.php on line 31

kome lo dovrei correggere??

<?php

if (!empty($_POST['inviadati']) )  {
//if ($_POST['inviadati']==true){

$dominio = $_POST['dominio'];
$spazio = $_POST['spazio'];
$hosting =  $_POST['hosting'];
$scad_dominio =  $_POST['scad_dominio'];
$importo_hosting =  $_POST['importo_hosting'];
//$scad_hosting =  $_POST['scad_hosting'];
$user_ftp =  $_POST['user_ftp'];
$pass_ftp =  $_POST['pass_ftp'];
$host =  $_POST['host'];


    include ("connessione.php");
    connect_to_ecom_db();

    include ("errore.php");
    
    // lego la variabile $oggetto all'oggetto in sessione
    //session_start();
    //$id = $_SESSION['idcliente'];
    $id =1;
    
    $sql="INSERT INTO scadenze_domini (dominio, spazio, hosting, importo_hosting, scadenza_dominio, host, user_ftp, pass_ftp,idcliente ) VALUES ('$dominio', '$spazio','$hosting','$importo_hosting','$scad_dominio','$host','$user_ftp','$pass_ftp',$id)";
    $query =mysql_query ($sql) or die (errore_server());
    header("Location: promemo.php");
    
}
 
?>