form values not changing

Maybe there's something that I just don't get but here's the problem I'm having. I use this piece of code to initialize the text box in a form: Address: <input type="text" name="x_Address" size="20" <?php if (isset($_SESSION['x_Address'])) echo "value=\"$_SESSION[x_Address]\""?>> Then I have a little php processing page that stores this value in a session variable and it just does it like this: echo $x_Address; $_SESSION['x_Address'] = $x_Address; I added the echo to check and make sure it was working but it doesn't change the value when I resubmit the form. When I first load up the page it's blank and when I hit back it fills in all the fields right, but then when I resubmit the form with new values they're all just the ones from the first time that I submitted the form. Is there something that I'm doing wrong? Thanks, Dave