You are trying to mix GET (sending parameters through the query string) with POST (sending them through a form with method=post). You have to choose one or the other.
If you want to send data through a form instead of a link, make “some” a hidden field.
<input type="hidden" name="some" value="<?php echo $num; ?>" />
And I’ll assume when you said $some, you meant $_GET[‘some’], but with the above form it’ll be in $_POST[‘some’].