Rabea
You need to specify the method of your form to post in order to use the $POST array (much like you have with the $GET array)
Another important point to note is that by default a form will use a method of GET if none is specified and will therefore only be able to pass a certain number of characters (i forget how much).
Simply change the form method to post and then use the $_POST (or to ensure total compatibility use $HTTP_POST_VARS)
HTH
Gary Mailer