// ******** AGGIORNA ************************************************************************************************************************************************
    function getUsers(){
        $vUsers = array ();
        $res = mysql_query ("SELECT * FROM security");
        $num = mysql_num_rows($res);
        for ($i = 0; $i < $num; $i++){
            $vUsers [$i] = array("id"=>mysql_result($res,$i,0),
                                "data"=>mysql_result($res,$i,1),
                                "flag"=>mysql_result($res,$i,2));
        }
        mysql_free_result($res);
        return $vUsers;
    }

    function aggiorna(){
        $tempo = date('Y-m-d H:i:s');
        $tempo_log = date('Y-m-d H:i:s', strtotime('+5 minutes'));
        $users = getUsers();
            for ($i = 0; $i < count($users); $i++){
                if($users[$i]['data']>$tempo_log){
                    $id = $users[$i]['data'];
                    mysql_query("UPDATE security SET logged_in = '0' WHERE id_user = '$id'");
                }
            }
            if ($_SESSION['AUTH'] != NULL){
                $user = $_SESSION['AUTH']['id'];
                mysql_query ("UPDATE security SET data_login = '$tempo' WHERE id_user = '$user'");
            }
    }

// ******************************************************************************************************************************************************************

// ******** VALIDATE ************************************************************************************************************************************************

function validateUser ($username,$password){
        $res = mysql_query ("SELECT * FROM users WHERE Username LIKE '$username' AND Password = '$password'");
        $num = mysql_num_rows($res);
        if ($num == 1){
            $user = array("id" => mysql_result($res,0,0),
                           "type" => mysql_result($res,0,1),
                           "username" => mysql_result($res,0,2),
                           "email" => mysql_result($res,0,4));
            $id = $user["id"];
            $flag = mysql_query ("SELECT logged_in FROM security WHERE id_user ='$id'");
            $flag1 = mysql_result($flag,0,0);
            if($flag1 == 1){
                    return NULL;
            }else{
                    mysql_free_result($res);
                    return $user;
                    }
        }
        else return NULL;

    }

// ******************************************************************************************************************************************************************



// ******** LOG *****************************************************************************************************************************************************

    $_SESSION['AUTH'] = validateUser($_POST['username'],$_POST['password']);
    $user = $_SESSION['AUTH']['id'];
    $tempo = date('Y-m-d H:i:s');
    mysql_query("UPDATE security SET logged_in = '1', data_login = '$tempo' WHERE id_user = '$user'");
    header ("Location: ".$_SERVER['HTTP_REFERER']);

// ******************************************************************************************************************************************************************