Untitled

<?php
header('Content-type: text/html; charset=utf-8');
error_reporting(E_ALL);
session_start();
$users = array('stas' => '40bd001563085fc35165329ea1ff5c5ecbdbbeef');

$codes = unserialize(file_get_contents('touch.txt');


if(empty($_SESSION['username']))
{
    if(empty($_POST['ok']))
    {
        $content = '<label>Логин<input name="username"></label><br>
                    <label>Пароль<input type="password" name="password"></label><br>
                    <input type="submit" name="ok" value="Во имя Стаса!!!">';
    }
    else
    {
        foreach($users as $username => $password)
            if($username == $_POST['username'] && $password == sha1($_POST['password']))
                $_SESSION['username'] = $username;

        if(empty($_SESSION['username']))
        {
            header('HTTP/1.1 404 Not Found');
            die('404');
        }
        else
            header('location: ' . $_SERVER['HTTP_REFERER']);
    }
}
else
{
    if(!empty($_POST['leave']))
    {
        session_unset();
        session_destroy();
        header('location: ' . $_SERVER['HTTP_REFERER']);
    }
    if(empty($_POST['role']))
    {
        $content = 'Welcome home, ' . $_SESSION['username'] . '! Choose your fate<br>
                    <input type="submit" name="role" value="admin">&nbsp
                    <input type="submit" name="role" value="student">&nbsp
                    <input type="submit" name="role" value="teacher">&nbsp';
    }
    else
    {
        if(!empty($_POST['code']) && !empty($_POST['role']) && array_key_exists($_POST['role'], $codes))
        {
            if($codes[$_POST['role']] == sha1($_POST['code']))
                $content = '42';
            else
            {
                header('HTTP/1.1 404 Not Found');
                die('404');
            }
        }
        else
        {
            $content = 'Для получения доступа к источнику вечной радости и вселенской мудрости введите сверхсекретный суперкод<br>
                        <input type="password" name="code">
                        <input type="hidden" name="role" value="' . $_POST['role'] . '">
                        <input type="submit" name="ok" value="Заглотнуть космической энергии">';
        }
    }
    $content .= '<input type="submit" name="leave" value="пс, парень, не хочешь начать с чистого листа?" style="position: absolute; right: 0; top: 0">';
}
?>
<!DOCTYPE html>
<html>
<head>
    <title>Стас ван лав!!!11 <333</title>
</head>
<body style="text-align: center; padding-top: 200px">
    <form action="" method="post">
        <?php echo $content; ?>
    </form>
</body>
</html>