session vars with recursive form

How can I correctly register session vars on a recursive form? If I call a page repeatedly using: <FORM ACTION="<?php echo $PHP_SELF ?>" METHOD="POST"> The earlier variables keep getting lost. How can I register the session variables correctly? Each subsequent page should set its own variable while remembering all those previously set. Right now the top of the page says: ----------- session_start(); $thevals=array(alpha,beta,gamma,delta,epsilon); while (list($key, $val) = each($thevals)) { if (!session_is_registered($val) ) { session_register("$val"); } } ---------- thanks, bill