Ho questi file per dare all'amministratore del sistema la possibilità di dare i permessi agli utenti.
con il primo file utenti_ins crea un nuovo utente assegnandogli username e password,
poi passa ad utenti_ins2 dove gli assegna i permessi.
Il problema è che se per un qualsiasi motivo fa il refresh della pagina utenti_ins2 invia nuovamente i dati a mysql.
Come posso fare per evitare questa cosa?

utenti_ins
Codice PHP:
<?php session_start();
if ($_SESSION['login_staff'] != "ok")  { 
    header("Location: login.php");
    exit;
} else {
    $_SESSION['setta'] = "utenti";
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1">
<meta name="generator" content="">
<?php
include("top_foot.inc.php"); 
?>
</head>
<body>
    <div id="header">
    <?php /* testata */
    top();
    ?>
    <?php /* menusuperiore */
    barra();
    ?>
    </div>
        <div id="navigation">
        <?php include "menu_sx_bk.php"; ?>
        </div>
<div id="content">
<table width="760" border="0" align="center" cellpadding="0" cellspacing="0">
    <td width="610" valign="top"> 
      <?php if (checkpermessi("inserimento","utenti",$_SESSION['login_staff_utente'])) { ?>
      

      <table width="600" border="0" align="center" cellpadding="0" cellspacing="0">
        <tr>
          <td align="center" valign="top"> 
          <form action="utenti_ins2.php" method="post" name="form" onSubmit="return validateForm(this);">
              <table width="550" height="30" border="0" cellpadding="0" cellspacing="0">
                <tr> 
                  <td align="center" valign="middle">[b]<font color="#000000">Inserimento 
                    Nuovo Utente</font>[/b]</td>
                </tr>
              </table>
              

              <table width="500" border="0" cellpadding="0" cellspacing="0">
                <tr> 
                  <td valign="top"> 
                    <div align="center"> 
                      <table border="0" cellspacing="0" cellpadding="0">
                        <tr> 
                          <td> <div align="center"> 
                              <table border="0" cellpadding="5" cellspacing="0">
                                <tr> 
                                  <td align="right"> Username </td>
                                  <td> <input name="username" type="text" id="username" size="15" maxlength="10"> 
                                  </td>
                                </tr>
                                <tr> 
                                  <td align="right">Password </td>
                                  <td> <input name="password" type="text" size="15" maxlength="10"> 
                                  </td>
                                </tr>
                                <tr> 
                                  <td align="right">Tipo  </td>
                                  <td> 
<?php $tipi = array("admin","redattore"); ?>
<select name="tipo" id="tipo">
<?php foreach ($tipi as $ti) {
    print "<option value=".$ti.">".ucfirst($ti)."</option>";    
    }
?>
</select> </td>
                                </tr>
                              </table>
                              

                              <input name="submit" type=submit value="continua">
                              

                              

                            </div></td>
                        </tr>
                      </table>
                      

                      

                      

                    </div></td>
                </tr>
              </table>
              

              </form>



          </td>
        </tr>
      </table>
<?php } else {
    header("Location: index.php");
    exit;
}
?>
    </td>
  </tr>
</table>
</div>
                    <div id="footer">
                    <?php /* footer */
                    foot();
                    ?>
                    </div>
</body>
</html>
<?php } ?>

che mi manda al file utenti_ins2

<?php session_start();
if ($_SESSION['login_staff'] != "ok")  { 
    header("Location: login.php");
    exit;
} else {
    $_SESSION['setta'] = "utenti";
    include "connect.php";
?>
<?php $query = mysql_query("INSERT INTO utenti (username,password,tipo) VALUES ('".$username."','".$password."','".$tipo."')"); ?>
<?php if ($tipo == "admin") {
    header("Location: utenti_lista.php");
    exit;
} else {
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1">
<meta name="generator" content="">
<?php
include("top_foot.inc.php"); 
?>
</head>
<body>
    <div id="header">
    <?php /* testata */
    top();
    ?>
    <?php /* menusuperiore */
    barra();
    ?>
    </div>
        <div id="navigation">
        <?php include "menu_sx_bk.php"; ?>
        </div>
<div id="content">

<table width="760" border="0" align="center" cellpadding="0" cellspacing="0">
  <tr valign="top"> 
    <td width="610" valign="top"> 
      <?php if (checkpermessi("inserimento","utenti",$_SESSION['login_staff_utente'])) { ?>
      

      <table width="600" border="0" align="center" cellpadding="0" cellspacing="0">
        <tr>
          <td align="center" valign="top"> 
          <form action="utenti_ins3.php" method="post" name="form">
              <table width="550" height="30" border="0" cellpadding="0" cellspacing="0">
                <tr> 
                  <td align="center" valign="middle">[b]<font color="#000000">Inserimento 
                    Nuovo Utente</font>[/b]</td>
                </tr>
              </table>
              <table width="500" border="0" cellpadding="0" cellspacing="0">
                <tr> 
                  <td> <div align="center"> 
                      <table border="0" cellpadding="5" cellspacing="0">
                        <tr> 
                          <td align="right"> Username </td>
                          <td> [b] 
                            <input name="username" type="hidden" id="username" value="<?php print "$username"; ?>">
                            <?php print stripslashes("$username"); ?>[/b]</td>
                        </tr>
                        <tr> 
                          <td align="right">Password </td>
                          <td>[b] 
                            <input name="password" type="hidden" id="password" value="<?php print "$password"; ?>">
                            <?php print "$password"; ?> [/b]</td>
                        </tr>
                        <tr> 
                          <td align="right">Tipo  </td>
                          <td> [b] 
                            <input name="tipo" type="hidden" id="tipo" value="<?php print "$tipo"; ?>">
                            <?php print "$tipo"; ?> [/b]</td>
                        </tr>
                      </table>
                      

                    </div></td>
                </tr>
              </table>
              <?php if ($tipo != "admin") { ?>
              

              [b]Inserimento Permessi Utente[/b]

              

              
              <?php $aree = array("utenti","news","appuntamenti","convegni","eventi","rassegna","bacheca","registrazione","circolari"); ?>
              <table border="0" cellspacing="1" cellpadding="1">
                <tr bgcolor="#ff0000">
                  <td width="150" height="20">[b]<font color="#FFFFFF"> Aree di gestione[/b]</td>
                  <td width="70" height="20" align="center">[b]<font color="#FFFFFF"> Inserisci[/b]</td>
                  <td width="70" height="20" align="center">[b]<font color="#FFFFFF">  Modifica[/b]</td>
                  <td width="70" height="20" align="center">[b]<font color="#FFFFFF">  Elimina[/b]</td>
                  <td width="70" height="20" align="center">[b]<font color="#FFFFFF">  Visualizza[/b]</td>
                </tr>
                <?php foreach ($aree as $area) { ?>
                <tr bgcolor="#ffcc00"> 
                  <td width="150">[b]<?php print strtr(ucfirst($area),"_"," "); ?>[/b]</td>
                  <td width="70" align="center"><?php print "<input name=".$area."_inserisci " . " type=checkbox id=".$area."_inserisci " . "value=ok>"; ?></td>
                  <td width="70" align="center"><?php print "<input name=".$area."_modifica " . " type=checkbox id=".$area."_modifica " . "value=ok>"; ?></td>
                  <td width="70" align="center"><?php print "<input name=".$area."_elimina " . " type=checkbox id=".$area."_elimina " . "value=ok>"; ?></td>
                  <td width="70" align="center"><?php print "<input name=".$area."_visualizza " . " type=checkbox id=".$area."_visualizza " . "value=ok>"; ?></td>
                </tr>
                
                <?php } ?>
              </table>
              

              <?php } ?>
              

              <input name="submit" type=submit value="continua">
              

              

            </form>
            


          </td>
        </tr>
      </table>
<?php } else {
    header("Location: index.php");
    exit;
}
?>
    </td>
  </tr>
</table>
</div>
                    <div id="footer">
                    <?php /* footer */
                    foot();
                    ?>
                    </div>
</body>
</html>
<?php }} ?>

che passando al file utenti_ins3 mi salva i dati

<? session_start();
if ($_SESSION['login_staff'] != "ok")  { 
    header("Location: login.php");
    exit;
} else {
    $_SESSION['setta'] = "utenti";
    include "connect.php";


    $query = mysql_query("SELECT idutente FROM utenti WHERE username = '".$username."'");
    $row = mysql_fetch_array($query);
    $id = $row['idutente'];

    // inserisci permessi
    $aree = $aree = array("utenti","news","appuntamenti","convegni","eventi","rassegna","bacheca","registrazione","circolari");
    foreach ($aree as $area) {


$ck_ins = "$area"."_inserisci";
$ck_mod = "$area"."_modifica";
$ck_can = "$area"."_elimina";
$ck_vis = "$area"."_visualizza";

$$ck_ins = isset($$ck_ins);    
$$ck_mod = isset($$ck_mod);
$$ck_can = isset($$ck_can);
$$ck_vis = isset($$ck_vis);    

        if ($$ck_ins == "ok") { mysql_query("INSERT INTO permessi (idutente,sezione,azione) VALUES (".$id.",'".$area."','inserimento')"); }
        if ($$ck_mod == "ok") { mysql_query("INSERT INTO permessi (idutente,sezione,azione) VALUES (".$id.",'".$area."','modifica')"); }
        if ($$ck_can == "ok") { mysql_query("INSERT INTO permessi (idutente,sezione,azione) VALUES (".$id.",'".$area."','elimina')"); }
        if ($$ck_vis == "ok") { mysql_query("INSERT INTO permessi (idutente,sezione,azione) VALUES (".$id.",'".$area."','visualizza')"); }
   }

  
    header("Location: utenti_lista.php");
    exit;

} ?>