Thanks for the replies everyone. The problem seems to have been that the script on the CD had missing code from it. By following the example in the book itself, I added the following code and got it to work:
$tireqty = $_POST ['tireqty'];
$oilqty = $_POST ['oilqty'];
$sparkqty = $_POST ['sparkqty'];
Later in the book, better methods are discussed in the regex section.
Register_globals is discussed, although the book says never to use it due to security risks. The book uses 5.3 when it was still available.
The mysql API database connector used in the book is mysqli .
Will this book still do for the basics, do you think?