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

654 Chapter 29 Building a Web-Based Email Service
Solution Overview
The general flow through this web-based system isn’t much different from other email
clients. Figure 29.1 shows a diagram illustrating the system flow and modules.
Login
Set up
account
Select
Account
View
mailbox
New
mail
Logout
View
message
Reply
Reply
all
Forward
Delete
Show/hide
headers
Figure 29.1
The interface for Warm Mail gives the user mailbox-level functionality
and message-level functionality.
As you can see, you first require a user to log in and then give him a choice of options.
He can set up a new mail account or select one of his existing accounts for use. He also
can view his incoming mail—responding to, forwarding, or deleting it—and send new
mail.
You also give the user 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.
This project uses a slightly different application architecture. Instead of having a set of
scripts, one for each module, this project has a slightly longer script, index.php, that
works like the event loop of a GUI-driven program. Each action taken on the site by
clicking a button brings you back to index.php, but with a different parameter.
Depending on the parameter, different functions are 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 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 29.1.