Chapter 17. Three Tiers
In this chapter we drive the golden spike that connects the user -interface code of the last few chapters with the database technology that preceded it. In this chapter we finally create a true three-tiered application with solid client, application, and back-end software.
In the past few chapters we have built a password checking system. However, it would be an absurd architecture to make a system that required changing the codebase every time a new user was added (though perhaps it would be one way of assuring job security). Instead, we use a MySQL database to store the account information and use PHP middleware to retrieve the data.
Working in such a model is an excellent example of a three-tiered solution (Figure 17.1). We have the first tier, the client-side Flash, which then works its way up the line (via XML) to our middle tier, PHP. The PHP binds the first tier to the third, our MySQL database.
Figure 17.1. Three-Tier Design