Sto inserendo con un include un file che contiene questo codice:
Codice PHP:
<?php
//ricordarsi che in locale la cartella si scrive cosi: /tmp
//sul server è tmp/
ini_set('session.save_path','../tmp'); 
session_start();
?>
<?php
// include server parameters
  require('includes/configure.php');
?>
<?php
    if (!empty($_POST['user']) and !empty($_POST['password'])) {     
                $pass = md5($_POST['password']); 
                $user = $_POST['user'];
                    
                $sql = "SELECT * FROM users WHERE user = '$user' AND password = '$pass'";
                $consulta=mysql_query($sql,$conn);            
                $nom=mysql_num_rows($consulta);
                                
                if ($nom==1) {                
                    $_SESSION['valido'] = "strSessionOK";     
                    header("Location: main.php");
                } else {                
                    $_SESSION['valido'] = "strSessionDenied";
                    $error = " Errore: Nome e Password non validi.";
                }
            } else {
        
        if (!isset($_SESSION['valido'])){    
            $_SESSION['valido'] = "strSessionDenied";    
        } 
        $error = "";
    }

?>
<? echo $error; ?>
<form method="get" name="login" id="login">
  <input name="user" type="text" class="login" value="user" />
  <input name="password" type="text" class="login" value="password" />
  <input name="Submit" type="submit" class="login" onClick="javascript:caricaBox('boxes/login.php', 'utente');return false;" value="Ok" />
</form>
Il file viene incluso in un punto della index, ma se testo la pagina mi da questo errore in quel punto:
Warning: session_start() [function.session-start]: open(../tmp\sess_adbc1c445fc8c0db91b0ec0088585d2d, O_RDWR) failed: No such file or directory (2) in C:\xampp\htdocs\siti\ilcaianello\boxes\login.php on line 5

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at C:\xampp\htdocs\siti\ilcaianello\index.php:7) in C:\xampp\htdocs\siti\ilcaianello\boxes\login.php on line 5

grazie