when you post a form, you can post it to another php script like so...
<form enctype="multipart/form-data" action="newreply.php" method="post">
the script "newreply.php" now can read the variables passed into it from the form. for example, if you have a text field in the html form with the attribute "name='firstname'", then the newrelpy.php script now has access to the variable $firstname, containing the data entered in that field in the form.
so you can use the target script to manipulate the values...