7. Form Handling
Any time you need to gather information from the users of your Web sites, you’ll need to use a form.
Forms can contain most of the usual graphical interface elements, including entry fields, radio buttons, check boxes, pop-up menus, and entry lists. In addition, HTML forms can contain password fields, shielding the user’s input from prying eyes.
Once the form is filled out, a click on the form’s Submit button sends the form’s information to your Web server, where a CGI (that stands for Common Gateway Interface, and it’s a script that runs on the Web server) interprets the data and acts on it. Often, the data is then stored in a database for later use. It’s useful to make sure that the data the user enters is “clean,” that is, ...