PHP/MySQL: Get value from one field, subtract 2, multiply by 20, and insert value into another column on form submit

Question

Hello all,
I'm pulling my hair out--thank you for any help you can give
me.
I have a form that a person fills out that has a field that
asks "How
many visitors including you" and I'd like them to type in a
number, and
on submit of the form, have that value -2 multiplied by 20
and inserted
into a "total cost" column.
I'm using the standard DW server behaviors and I've searched
the
internet. How do I perform basic math on that value and
insert it into
the database?
If you have any pointers, that would be great.
Thank you!
-John

Answer 1

John R. Lenz wrote:
> Your code below works great, and I just noticed links to
your book were
> available on your web site, and it's in the mail to me.
Looking forward
> to it.
Thanks, hope you find it useful.
> After the form is posted, I'd like to address the person
who posted it
> by their first name and last name, as well as some of
the details. How
> would you go about doing this in the best way? Would you
set a variable
> and echo it on the 'Thank you' page, or are there better
ways of doing
> it with a recordset and filtering it on form submit?
To pass the details to a thank you page, you would need to
store the
information in $_SESSION variables. You could amend the
earlier script
like this:
<?php
session_start();
if (isset($_POST['visitors'])) {
if ($_POST['visitors'] < 3) {
$num = 0;
} else {
$num = $_POST['visitors'] - 2;
$_POST['total_cost'] = $num * 20;
$_SESSION['total_cost'] = $_POST['total_cost'];
$_SESSION['first_name'] = $_POST['first_name'];
$_SESSION['last_name'] = $_POST['last_name'];
?>
In the thank you page, put the following at the top of the
page:
<?php session_start(); ?>
It must go before anything is output to the browser, so put
it above the
DOCTYPE declaration, and make sure there's no space before
it.
You can then use the $_SESSION variables in the thank you
page.
At the end of the page, add this to clear up the session
variables:
<?php
$_SESSION = array();
destroy_session();
?>
David Powers, Adobe Community Expert
Author, "The Essential Guide to Dreamweaver CS3" (friends of
ED)
Author, "PHP Solutions" (friends of ED)
http://foundationphp.com/