Specifications

We will also give him the option of viewing detailed headers for a particular message. Viewing

the complete headers can tell you a lot about a message. You can see which machine the mail

came from—a useful tool for tracking down spam. You can see which machine forwarded it

and at what time it reached each host—useful for assigning blame for delayed messages. You

might also be able to see which email client the sender used if the application adds optional

information to the headers.

We have used a slightly different application architecture for this project. Instead of having a

set of scripts, one for each module, we have a slightly longer script, index.php, that works like

the event loop of a GUI-driven program. Each action we take on the site by pressing a button

will bring us back to index.php, but with a different parameter. Depending on the parameter,

different functions will be called to show the appropriate output to the user. The functions are

in function libraries, as usual.

This architecture is suitable for small applications such as this. It suits applications that are

very event driven, where user actions trigger functionality. Using a single event handler is not

very suitable for larger architectures or projects being worked on by a team.

A summary of the files in the Warm Mail project is shown in Table 27.1.

TABLE 27.1 Files in the Warm Mail Application

Name Type Description

index.php Application The main script that runs the entire application

include_fns.php Functions Collection of include files for this application

data_valid_fns.php Functions Collection of functions for validating input data

db_fns.php Functions Collection of functions for connecting to the

mail database

mail_fns.php Functions Collection of email-related functions for open-

ing mailboxes, reading mail, and so on

output_fns.php Functions Collection of functions for outputting HTML

user_auth_fns.php Functions Collection of functions for authenticating users

create_database.sql SQL SQL to set up the book_sc database and set up

a user

Let’s go ahead and look at the application.

Building a Web-Based Email Service

HAPTER 27

BUILDING A

WEB-BASED

SERVICE

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