ho sostituito alla pagina dove registro le sessioni cosi
codice:
<?php
session_start();

$loginFormAction = $_SERVER['PHP_SELF'];
if (isset($accesscheck)) {
  $_SESSION['PrevUrl'] = $accesscheck;
}


if (isset($_POST['user'])) {
  $loginUsername=$_POST['user'];
  $password=$_POST['pw'];
  $MM_fldUserAuthorization = "";
  $MM_redirectLoginSuccess = "rivenditori/autenticato.php";
  $MM_redirectLoginFailed = "rivenditori/fallito.php";
  $MM_redirecttoReferrer = false;
  mysql_select_db($database_conn, $conn);
  
  $LoginRS__query=sprintf("SELECT ragionesociale, partitaiva FROM clienti WHERE ragionesociale='%s' AND partitaiva='%s'",
    get_magic_quotes_gpc() ? $loginUsername : addslashes($loginUsername), get_magic_quotes_gpc() ? $password : addslashes($password)); 
   
  $LoginRS = mysql_query($LoginRS__query, $conn) or die(mysql_error());
  $loginFoundUser = mysql_num_rows($LoginRS);
  if ($loginFoundUser) {
     $loginStrGroup = "";
    
   
    $GLOBALS['MM_Username'] = $loginUsername;
    $GLOBALS['MM_UserGroup'] = $loginStrGroup;	      

   
    session_register("MM_Username");
    session_register("MM_UserGroup");

    if (isset($_SESSION['PrevUrl']) && false) {
      $MM_redirectLoginSuccess = $_SESSION['PrevUrl'];	
    }
    header("Location: " . $MM_redirectLoginSuccess );
  }
  else {
    header("Location: ". $MM_redirectLoginFailed );
  }
}
?>
mentre questo è il codice della pagina che mi respinge (a cui non riesco ad accedere)
codice:
<?php
session_start();
$MM_authorizedUsers = "";
$MM_donotCheckaccess = "true";

function isAuthorized($strUsers, $strGroups, $UserName, $UserGroup) { 
  $isValid = False; 
  if (!empty($UserName)) { 
    $arrUsers = Explode(",", $strUsers); 
    $arrGroups = Explode(",", $strGroups); 
    if (in_array($UserName, $arrUsers)) { 
      $isValid = true; 
    } 
    if (in_array($UserGroup, $arrGroups)) { 
      $isValid = true; 
    } 
    if (($strUsers == "") && true) { 
      $isValid = true; 
    } 
  } 
  return $isValid; 
}

$MM_restrictGoTo = "../fallito.php";
if (!((isset($_SESSION['MM_Username'])) && (isAuthorized("",$MM_authorizedUsers, $_SESSION['MM_Username'], $_SESSION['MM_UserGroup'])))) {   
  $MM_qsChar = "?";
  $MM_referrer = $_SERVER['PHP_SELF'];
  if (strpos($MM_restrictGoTo, "?")) $MM_qsChar = "&";
  if (isset($QUERY_STRING) && strlen($QUERY_STRING) > 0) 
  $MM_referrer .= "?" . $QUERY_STRING;
  $MM_restrictGoTo = $MM_restrictGoTo. $MM_qsChar . "accesscheck=" . urlencode($MM_referrer);
  header("Location: ". $MM_restrictGoTo); 
  exit;
}

function pre($array) {
 if(empty($array)) {
   echo "array inesistente";
 }
echo "<pre>";
print_r($array);
echo "</pre>";
}
pre($_SESSION);

?>
ma continua e negarmi l'accesso (solo su aruba mentre in locale funziona)