problema login,utente si disconnette

[enea86]

<?php
$_CONFIG['host'] = "localhost";
$_CONFIG['user'] = "******";
$_CONFIG['pass'] = "********";
$_CONFIG['dbname'] = "miodb";

$_CONFIG['table_sessioni'] = "sessioni";
$_CONFIG['table_utenti'] = "utenti";

$_CONFIG['expire'] = 60;


//--------------
define('AUTH_LOGGED', 99);
define('AUTH_NOT_LOGGED', 100);

define('AUTH_USE_COOKIE', 101);
define('AUTH_USE_LINK', 103);
define('AUTH_INVALID_PARAMS', 104);
define('AUTH_LOGEDD_IN', 105);
define('AUTH_FAILED', 106);

$conn = mysql_connect($_CONFIG['host'], $_CONFIG['user'], $_CONFIG['pass']) or die('Impossibile stabilire una connessione');
mysql_select_db($_CONFIG['dbname']);
?>

<?php

$_AUTH = array(
    "TRANSICTION METHOD" => AUTH_USE_COOKIE
);

function auth_set_option($opt_name, $opt_value){
    global $_AUTH;
    
    $_AUTH[$opt_name] = $opt_value;
}

function auth_get_option($opt_name){
    global $_AUTH;
    
    return is_null($_AUTH[$opt_name])
        ? NULL
        : $_AUTH[$opt_name];
}

function auth_clean_expired(){
    global $_CONFIG;
    
    $result = mysql_query("SELECT creation_date FROM ".$_CONFIG['table_sessioni']." WHERE uid='".auth_get_uid()."'");
    if($result){
        $data = mysql_fetch_array($result);
        if($data['creation_date']){
            if($data['creation_date'] + $_CONFIG['expire'] <= time()){
                switch(auth_get_option("TRANSICTION METHOD")){
                    case AUTH_USE_COOKIE:
                        setcookie('uid');
                    break;
                    case AUTH_USE_LINK:
                        global $_GET;
                        $_GET['uid'] = NULL;
                    break;
                }
            }
        }
    }
    
    mysql_query("
    DELETE FROM ".$_CONFIG['table_sessioni']."
    WHERE creation_date + ".$_CONFIG['expire']." <= ".time()
    );
}

function auth_get_uid(){
    
    $uid = NULL;

    switch(auth_get_option("TRANSICTION METHOD")){
        case AUTH_USE_COOKIE:
            global $_COOKIE;
            $uid = $_COOKIE['uid'];
        break;
        case AUTH_USE_LINK:
            global $_GET;
            $uid = $_GET['uid'];
        break;
    }

    return $uid ? $uid : NULL;
}

function auth_get_status(){
    global $_CONFIG;

    auth_clean_expired();
    $uid = auth_get_uid();
    if(is_null($uid))
        return array(100, NULL);
    
    $result = mysql_query("SELECT U.name as name, U.surname as surname, U.username as username
    FROM ".$_CONFIG['table_sessioni']." S,".$_CONFIG['table_utenti']." U
    WHERE S.user_id = U.id and S.uid = '".$uid."'");
    
    if(mysql_num_rows($result) != 1)
        return array(100, NULL);
    else{
        $user_data = mysql_fetch_assoc($result);
        return array(99, array_merge($user_data, array('uid' => $uid)));
    }
}

function auth_login($uname, $passw){
    global $_CONFIG;

    $result = mysql_query("
    SELECT *
    FROM ".$_CONFIG['table_utenti']."
    WHERE username='".$uname."' and password=MD5('".$passw."')"
    );
    
    if(mysql_num_rows($result) != 1){
        return array(AUTH_INVALID_PARAMS, NULL);
    }else{
        $data = mysql_fetch_array($result);
        return array(AUTH_LOGEDD_IN, $data);
    }
}

function auth_generate_uid(){

    list($usec, $sec) = explode(' ', microtime());
    mt_srand((float) $sec + ((float) $usec * 100000));
    return md5(uniqid(mt_rand(), true));
}

function auth_register_session($udata){
    global $_CONFIG;
    
    $uid = auth_generate_uid();
    
    mysql_query("
    INSERT INTO ".$_CONFIG['table_sessioni']."
    (uid, user_id, creation_date)
    VALUES
    ('".$uid."', '".$udata['id']."', ".time().")
    "
    );
    if(!mysql_insert_id()){
        return array(AUTH_LOGEDD_IN, $uid);
    }else{
        return array(AUTH_FAILED, NULL);
    }
}

function auth_logout(){
    global $_CONFIG;

    $uid = auth_get_uid();
    
    if(is_null($uid)){
        return false;
    }else{
        mysql_query("
        DELETE FROM ".$_CONFIG['table_sessioni']."
        WHERE uid = '".$uid."'"
        );
        return true;
    }
}
?>

ecco i due files...
sono quelli che ho scaricato con la guida comunque.

grazie se mi potete dare una mano