PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

700 Chapter 30 Building a Mailing List Manager
You can see the four segments of the code clearly marked in this listing. In the preprocessing
stage, you set up the session and process any actions that need to be done before
headers can be sent. In this case, they include logging in and out.
In the header stage, you set up the menu buttons that the user will see and display the
appropriate headers using the do_html_header() function from output_fns.php.This
function just displays the header bar and menus, so we don’t discuss it in detail here.
In the main section of the script, you respond to the action the user has chosen.
These actions are divided into three subsets: actions that can be taken if not logged in,
actions that can be taken by normal users, and actions that can be taken by administrative
users.You check to see whether access to the latter two sets of actions is allowed by
using the check_logged_in() and check_admin_user() functions.These functions are
located in the user_auth_fns.php function library.The code for these functions and the
check_normal_user() function are shown in Listing 30.3.
Listing 30.3 Functions from user_auth_fns.php—These Functions Check Whether
a User Is Logged In and at What Level
function check_normal_user() {
// see if somebody is logged in and notify them if not
if (isset($_SESSION['normal_user'])) {
return true;
} else {
return false;
}
}
function check_admin_user() {
// see if somebody is logged in and notify them if not
if (isset($_SESSION['admin_user'])) {
return true;
} else {
return false;
}
}
function check_logged_in() {
return ( check_normal_user() || check_admin_user() );
As you can see, these functions use the session variables normal_user and admin_user
to check whether a user has logged in.We explain how to set up these session variables
shortly.