View file modile/adm/auth.php

<form name="" action="" method="post">
<input name="admin" type="text" value=""><br>
<input type="submit" value="Войти">
</form>
<?php
Defined('ADMIN_S_S') or die ('Доступ запрещен!!!');
if ($_POST['admin'] == '12345')
{
$_SESSION['user_login'] = 'admin';
}
?>