Php-Simple Cookie Login Script

<?php
extract($_REQUEST);

$user['some_username'];
$user['some_username']->password = 'some_password';

$phpself = $_SERVER['PHP_SELF'];

session_start();
$sessid = session_id();

if($action == "login" && $f_user != "" && $f_pass != "")
{
        if($user[$f_user]->password == $f_pass)
        {
                setcookie("sesser",md5($sessid . $f_user),time()+86400);
        }
        else
        {
                $rm = urlencode("Something went wrong while trying to log in.");
        }

        header("Location:{$phpself}?rm={$rm}&f_user={$f_user}"); exit();
}

if($action == "logout")
{
        setcookie("sesser",md5($sessid . $f_user),time()-1);
        header("Location:{$phpself}"); exit();
}
?>