Book Image

Modernizing Legacy Applications in PHP

By : Paul Jones
Book Image

Modernizing Legacy Applications in PHP

By: Paul Jones

Overview of this book

Have you noticed that your legacy PHP application is composed of page scripts placed directly in the document root of the web server? Or, do your page scripts, along with any other classes and functions, combine the concerns of model, view, and controller into the same scope? Is the majority of the logical flow incorporated as include files and global functions rather than class methods? Working with such a legacy application feels like dragging your feet through mud, doesn’t it?This book will show you how to modernize your application in terms of practice and technique, rather than in terms of using tools such as frameworks and libraries, by extracting and replacing its legacy artifacts. We will use a step-by-step approach, moving slowly and methodically, to improve your application from the ground up. We’ll show you how dependency injection can replace both the new and global dependencies. We’ll also show you how to change the presentation logic to view files and the action logic to a controller. Moreover, we’ll keep your application running the whole time. Each completed step in the process will keep your codebase fully operational with higher quality. When we are done, you will be able to breeze through your code like the wind. Your code will be autoloaded, dependency-injected, unit-tested, layer-separated, and front-controlled. Most of the very limited code we will add to your application is specific to this book. We will be improving ourselves as programmers, as well as improving the quality of our legacy application.
Table of Contents (35 chapters)
Modernizing Legacy Applications in PHP
Credits
Foreword
About the Author
Acknowledgement
www.PacktPub.com
Preface
Typical Legacy Page Script
Code before Gateways
Code after Gateways
Code after Transaction Scripts
Code before Collecting Presentation Logic
Code after Collecting Presentation Logic
Code after Response View File
Code after Controller Rearrangement
Code after Controller Extraction
Code after Controller Dependency Injection
Index

Embedded action logic


For an example of embedded action logic mixed with dependency logic, we can look at the ending example code from the last chapter in Appendix G, Code after Response View File. Therein, we do a little setup work, then we check some conditions and call different parts of our domain Transactions, and at the end we put together a Response object to send our response to the client.

As was the problem with mixed-in presentation logic, we cannot test the action logic separately from rest of the page script. Similarly, we cannot easily change the dependency creation logic to make the page script more testable.

We solve the problem of embedded action logic as we did with embedded presentation logic. We must extract the action code to a class of its own to separate the various remaining concerns of our page script. This will also allow us to test the action logic independently from the rest of the application.

The Extraction Process

Extracting the action logic from our page scripts...