Spayder,
if (file_exists(('../files/users/avatar/' . $user_id . '.png'))) {
echo '<img src="../files/users/avatar/' . $user_id . '.png" width="32" height="32" alt="' . $login . '" /> ';
} else {
echo '<img src="../images/empty.png" width="32" height="32" alt="ava" /> ';
}