shtml problem

I use a search.shtml script to pass with a form some vars (user's IP) to a PHP script to keep it in a MySQL record. When I run the search.shtml directrly , I have no problem all vars pass and are keept OK. But when I run it from a frame then the IP var is undefuned (null). --------------------------code for main.php ------------------- echo ('<table border=0><tr><td><iframe src="main_l.php" width=200 height=600 frameborder=0>'); echo ('</iframe></td><td><iframe src="search.shtml" width=780 height=600></iframe></td></tr></table>'); ------------------------------end code ----------------------------- What happens and what I can do? The dir is the same. Thanks Makis