Modernizing Legacy Applications in PHP by Jones, Paul M. -- Read -- Imperial Library of Trantor

Index

Modernizing Legacy Applications in PHP

Table of Contents Modernizing Legacy Applications in PHP Credits Foreword About the Author Acknowledgement www.PacktPub.com

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Preface 1. Legacy Applications

The typical PHP application

File Structure Page Scripts Rewrite or Refactor? The Pros and Cons of Rewriting Why Don't Rewrites Work?

The Context-switching problem The Knowledge problem The Schedule Problem Iterative Refactoring

Legacy Frameworks

Framework-based Legacy Applications Refactoring to a Framework

Review and next steps

2. Prerequisites

Revision control

PHP version Editor/IDE Style Guide

Test suite Review and next steps

3. Implement an Autoloader

PSR-0 A Single Location for Classes

Add Autoloader Code As a Global Function

As a Closure As a Static or Instance method

Using The __autoload() Function

Autoloader Priority

Common Questions

What If I Already Have An Autoloader? What are the Performance Implications Of Autoloading? How Do Class Names Map To File Names?

Review and next steps

4. Consolidate Classes and Functions

Consolidate Class Files

Find a candidate include Move the class file Remove the related include calls Spot check the codebase Commit, Push, Notify QA Do ... While

Consolidate functions into class files

Find a candidate include Convert the function file to a class file

Change function calls to static method calls Spot check the static method calls Move the class file

Do ... While

Common Questions

Should we remove the autoloader include call? How should we pick files for candidate include calls? What if an include defines more than one class? What if the one-class-per-file rule is disagreeable? What if a Class or Function is defined inline? What if a definition file also executes logic?

What if two classes have the same name?

What about third-party libraries?

What about system-wide libraries?

For functions, can we use instance methods instead of static methods?

Can we automate this process?

Review and next steps

5. Replace global With Dependency Injection

Global Dependencies

The replacement process Find a global variable Convert global variables to properties Spot check the class Convert global properties to constructor parameters

Convert instantiations to use parameters

Spot check, Commit, Push, Notify QA Do ... While

Common Questions

What if we find a global in a static method? Is there an alternative conversion process? What about class names in variables? What about superglobals? What about $GLOBALS?

Review and next steps

6. Replace new with Dependency Injection

Embedded instantiation The replacement process

Find a new keyword Extract One-Time creation to dependency injection Extract repeated creation to factory

Change instantiation calls

Spot Check, Commit, Push, Notify QA Do ... While Common Questions

What About Exceptions and SPL Classes? What about Intermediary Dependencies? Isn't this a lot of code? Should a factory create collections?

Can we automate all these Injections?

Review and next steps

7. Write Tests

Fighting test resistance The way of Testivus

Setting up a test suite

Install PHPUnit Create a tests/ directory Pick a class to test Write a test case Do ... While

Common Questions

Can we skip this step and do it later? Come On, Really, Can We Do This Later? What about hard-to-test classes? What about our earlier characterization tests? Should we test private and protected methods? Can we change a test after we write it? Do we need to test Third-party libraries? What about code coverage?

Review and next steps

8. Extract SQL statements to Gateways

Embedded SQL Statements

The extraction process Search for SQL statements

Move SQL to a Gateway class Namespace and Class names Method names

An initial Gateway class method

Defeating SQL Injection Write a test Replace the original code Test, Commit, Push, Notify QA Do ... While

Common Questions

What about INSERT, UPDATE, and DELETE Statements? What about Repetitive SQL strings? What about complex query strings? What about queries inside non-Gateway classes? Can we extend from a base Gateway class? What about multiple queries and complex result structures? What if there is no Database Class?

Review and next steps

9. Extract Domain Logic to Transactions

Embedded Domain Logic

Domain logic patterns

The Extraction Process

Search for uses of Gateway

Discover and Extract Relevant Domain Logic Example Extraction Spot check the remaining original code Write tests for the extracted transactions Spot check again, Commit, Push, Notify QA Do ... While

Common Questions

Are we talking about SQL transactions? What about repeated Domain Logic? Are printing and echoing part of Domain Logic? Can a transaction be a class instead of a Method? What about Domain Logic in Gateway classes? What about Domain logic embedded in Non-Domain classes?

Review and next steps

10. Extract Presentation Logic to View Files

Embedded presentation logic

The Extraction process

Search for Embedded presentation logic Rearrange the Page script and Spot Check

Extract Presentation to View file and Spot Check

Create a views/ Directory

Pick a View File name Move Presentation Block to View file

Add Proper Escaping

Write View File Tests

The tests/views/ directory

Writing a View File Test Asserting Correctness Of Content

Commit, Push, Notify QA Do ... While

Common Questions

What about Headers and Cookies?

What if we already have a Template system?

What about Streaming Content?

What if we have lots of Presentation variables?

What about class methods that generate output?

What about Business Logic Mixed into the presentation?

What if a page contains only presentation logic?

Review and next steps

11. Extract Action Logic to Controllers

Embedded action logic

The Extraction Process Search for Embedded Action Logic Rearrange the Page Script and Spot Check

Identify Code Blocks Move Code to Its Related Block Spot Check the Rearranged Code Extract a Controller Class Pick a Class Name Create a Skeleton Class File

Move the Action Logic and Spot Check Convert Controller to Dependency Injection and Spot Check

Write a Controller Test Commit, Push, Notify QA Do ... While

Common Questions

Can we pass parameters to the Controller method?

Can a Controller have Multiple actions? What If the Controller contains include Calls?

Review and next steps

12. Replace Includes in Classes

Embedded include Calls The Replacement process

Search for include Calls Replacing a Single include Call Replacing Multiple include Calls Copy include file to Class Method Replace the original include Call Discover coupled variables through testing Replace other include Calls and Test Delete the include file and test

Write a test and refactor Convert to Dependency Injection and test Commit, Push, Notify QA Do ... While

Common QuestionsCan one class receive logic from many include files? What about include calls originating in non-class files?

Review and next steps

13. Separate Public and Non-Public Resources

Intermingled resources The separation process

Coordinate with operations personnel Create a document root directory Reconfigure the server Move public resources Commit, push, coordinate

Common Questions

Is This Really Necessary?

Review and next steps

14. Decouple URL Paths from File Paths

Coupled Paths

The Decoupling Process Coordinate with Operations

Add a Front Controller Create a pages/ Directory

Reconfigure the Server

Spot check Move Page scripts Commit, Push, Coordinate

Common Questions

Did we really Decouple the Paths?

Review and next steps

15. Remove Repeated Logic in Page Scripts

Repeated logic

The Removal Process Modify the Front controller Remove Logic from Page Scripts Spot Check, Commit, Push, Notify QA Common Questions

What if the Setup Work Is Inconsistent? What if we used inconsistent naming?

Review and next steps

16. Add a Dependency Injection Container

What is a Dependency Injection Container?

Adding a DI Container Add a DI Container Include File

Add a Router Service Modify the Front Controller Extract Page Scripts to Services

Create a Container Service Route the URL Path to the Container Service Spot Check and Commit

Do ... While Remove pages/, Commit, Push, Notify QA

Common Questions

How can we refine our service definitions? What if there are includes In the Page Script? Can we reduce the size of the services.php file? Can we reduce the size of the router service? What if we cannot update to PHP 5.3?

Review and next steps

17. Conclusion

Opportunities for improvement Conversion to Framework Review and next steps

A. Typical Legacy Page Script B. Code before Gateways C. Code after Gateways D. Code after Transaction Scripts E. Code before Collecting Presentation Logic F. Code after Collecting Presentation Logic G. Code after Response View File H. Code after Controller Rearrangement I. Code after Controller Extraction J. Code after Controller Dependency Injection Index

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