CodeIgniter ignores changes in a included function

CodeIgniter ignores changes in a included function

I'm migrating a PHP app to CodeIgniter. In my header.php I include some
functions, one of them is a login form
set_include_path(dirname(__FILE__));
include(
DIRECTORY_SEPARATOR . '.config' .
DIRECTORY_SEPARATOR . 'login.php');
which is needed for
if(empty($_SESSION["login"]))
{
login_form();
}
In login.php I have
function login_form() {
echo "<div class=\"dowypelnienia\"><br /><br />Aby korzystaæ z serwisu,
musisz siê zalogowaæ:<br /><br />";
echo "<form action=\"index.php\" method=\"POST\" target=\"_self\"
enctype=\"multipart/form-data\">";
echo "Login: <input class=\"login_input\" focus name=\"login\" /> Has³o:
<input focus class=\"login_input\" name=\"password\" type=\"password\"
/>&nbsp;<input class=\"bold login_input\" type=\"submit\"
value=\"Zaloguj\" /></form>";
echo "</div>";
}
Now when I edit login_form() nothing changes, even when I erase it all.
The function still runs as if it wasn't edited at all so it must still
exist, but don't know where - cleaning browser's cache doesn't help. Error
shows up only after erasing include of login.php.

Can someone please explain this phenomenon?