How to store $_POST value permanently in PHP?

Question

Note sure how to explain this clearly but here is the problem:

I have a multi-page form process which takes the customer from a shopping cart page to a shipping page. On the cart page there is a hidden field called totalPrice which has as it's value an integer. I am calling this total on the shipping page like so:

$total = $_POST['totalCost'];
echo $total;

On this shipping page there is another form which asks the customer to choose a shipping method. When this form is submitted the totalCost is to be updated to reflect the added shipping cost.

I am trying to do that like this:

$total = $total + $shippingCost;

But this only shows the shipping cost when I echo $total again not the shipping added to the initial total. I guess that's because the form has been submitted and the initial $total hidden value carried on from the previous form is lost.

So Is there any way to make the initial totalPrice value permanent so that I can add the shipping cost to it as well?

Answer 1

Use session variables. http://php.net/manual/en/book.session.php

Answer 2

Use sessions!

session_start();
$_SESSION['data'] = $_POST['totalCost'];

http://lv.php.net/manual/en/session.examples.basic.php