This sample PHP program demonstrates the use of hidden fields to provide a session. This system involves a single PHP program, although this program can handle a number of different kinds of requests. The examples we have discussed in the past have involved multiple CGI programs, this one involves only one. The single PHP program (pizza.php) can act in different ways depending on the query received, specifically it looks at the form field named "formname" and does the following:

Value of formname	Resulting Action
none	Sends back a login form.
login	Validates the name and password, and if valid sends back an order form
order	Validates the order and if valid sends back a receipt

The system includes a login form that allows a user to log on to the system using a name and password. The PHP program simply checks for the username "joe" and the password "pizza", these values are part of the PHP program itself. In a real application this data would come from a file or a database...

Note: All the forms in this system use GET, in real life you would use POST for submission of a password!

Once the user logs in, the program sends back a pizza order form. When the order form is submitted, the order is processed only if the user's name and password are part of the request. The name and password are not entered by the user in the order form, instead these values come from hidden fields (created by the program when it created the order form).

This system uses hidden form fields to propogate state information between the login form and the order form. This means that the order form includes some hidden fields (name and password) so that it "knows" who it filling out the order form. As far as the program is concerened, it doesn't know whether the query is constructed by hand, or comes from a user who filled out the order form - as long as a name and password are present in the query the program will process the pizza order.

Keep in mind that using hidden fields does not provide a secure system! Any user could look at the HTML source for the order form and see what the name and password are!

Much of the HTML that is generated by the program is read from files. This makes it possible to change the look of the site without changing the PHP file.

---

FILES:

pizza.php	The PHP program. One program handles the entire system. Click on this link and you will get the login page. See below to actually see the source code.
logo	The WebSys Pizza logo that shows up on the top of all pages.
pizzaguy.gif	A graphic image included in the logo.
loginform.tmpl	The HTML form a user uses to log in to the pizza server.
orderform.tmpl	Most of the HTML form for ordering a pizza.
pizzaphp.html	Source code for the PHP program
pizza.zip	Zip file containing everything.