PHP & MySQL® Web Development All-in-One Desk Reference for Dummies®

3.4. Building the Login Script

The login application has one main login script that displays and processes the information from the login form. The script is organized into three basic sections:

• One section executes the first time the login page is displayed, before the user clicks a button.

• Another section executes when the user clicks the Login button.

• A third section executes when the user clicks the Register button.

A switch statement controls the script flow based on which button is clicked. The following is an overview of the structure of the script:

switch (Button)

  case "Login":
      1 Test whether the user name is in the database. If
        not, redisplay the form with an error message.
      2 Test whether the password is correct. If not,
        redisplay the form with an error message.
      3 When login succeeds, display the protected Web page.

  case "Register":
      1 Test whether all the fields are filled in. If not,
        redisplay the form with an error message.
      2 Test whether the information is in the correct
        format. If not, redisplay form with error message.
      3 When information is correct, store it in database.
      4 When registration succeeds, display the protected
        Web page.

  case "default":
      Display the Login Web Page with blank form fields

The default case executes if neither the Login button nor the Register button are clicked.

Listing 3-3 shows the code for the login application script.

Example 3.3. Login Application Code

<?php /* Program: Login_reg.php * Desc: Main application script for the User Login * ...