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

Consolidate functions into class files


Not all legacy applications use a large set of classes. Often, instead of classes, there is a significant number of user-defined functions for core logic.

Using functions is not a problem in itself, but it does mean that we need to include the files where the functions are defined. But autoloading only works for classes. It would be good to find a way to automatically load the function files as well as the class files. That would help us remove even more include calls.

The solution here is to move the functions into class files, and call the functions as static methods on those classes. That way, the autoloader can load up the class file for us, and then we can call the methods in that class.

This procedure is more complex than when we consolidated class files. Here is the general process we will follow:

  1. Find an include statement that pulls in a function definition file.

  2. Convert that function definition file into a class file of static methods; we need to...