PHP and Html referencing

[Anon]

I am new to PHP, and my question may be simple. I hava a PHP script that connects to a database and puts values from a certain table into hidden fields in a HTML form. what I want to know is. How can I the set the hidden fields to a new value in PHP script. This is only an example:
I have a hidden field like this:
<input type="hidden" name="INTERFACE_NARRATIVE" value="<? echo ${INTERFACE_NARRATIVE}; ?>">

Now I want to change the field value later in the html, through PHP or any other way that you may think of.

[Anon]

Do you want to do this without submiting the form?

if so you'll need to do it on the client, hence JavaScript

Bealers

[Anon]

yes I do want to do this before hitting submit.