Perl Cookbook

Writing a Multiscreen CGI Script

Problem

You want to write a single CGI script that can return several different pages to the browser. For instance, you want a single CGI script for administering a database of products. The script will be called to display the form to add a product, to process the add-product form, to display a list of products to delete, to process the delete-product form, to display a list of product to edit, to display a form of the product’s attributes for the user to change, and to process the edit-product form. You can use these multiscreen CGI scripts to form an elementary shopping-cart-type application.

Solution

Use a hidden field to encode the current screen.

Discussion

It is easy to generate sticky hidden fields with the CGI module. The hidden function returns HTML for a hidden widget and will use the widget’s current value if you only give hidden the widget name:

use CGI qw(:standard);
print hidden("bacon");

To determine which page (“display product list”, “display all items in shopping cart”, “confirm order”) to display, use another hidden field. We’ll call this one .State so it won’t conflict with any field we might have called State (for instance, in credit card billing information). To let the user move from page to page, use submit buttons that set .State to the name of the page to go to. For instance, to make a button to take the user to the “Checkout” page, use:

print submit(-NAME => ".State", -VALUE => "Checkout");

We wrap this in a function to make ...