Refactoring PHP Code: A Step-by-Step Guide

The book "Refactoring PHP Code" is a practical guide for developers who want to transform chaotic, hard-to-maintain code into a clean, extensible, and testable system. The author, Alexey Smirnov, with 10 years of experience in PHP, shares proven techniques and real-world cases from commercial development.

What is this book about?

You will learn how to safely and incrementally improve existing PHP code without the risk of breaking functionality. The book covers the full refactoring cycle: from analyzing "code smells" and setting priorities to implementing modern practices.

• Basics of Refactoring: what refactoring is, when it is needed, and when it is not. Analysis of antipatterns and "code smells" in PHP.
• Working with Legacy Code: how to safely introduce changes into old projects without tests. Techniques for extracting classes, breaking dependencies, and introducing interfaces.
• Architecture Refactoring: transitioning from spaghetti code to MVC, implementing Dependency Injection, working with service locators and factories.
• Working with Databases: refactoring SQL queries, data schema migrations, extracting repositories and Data Mapper.
• Testing: how to write tests for existing code, use mock objects, and perform refactoring under the protection of tests.
• Modern PHP: applying types, strict modes, generators, traits, and attributes (PHP 8+).

Who is this book for?

The book will be useful both for beginner PHP developers who want to write quality code from the start, and for experienced programmers working with legacy projects. It is especially recommended for:

• Developers maintaining old PHP 5/7 projects who want to migrate to PHP 8.
• Team leads and architects implementing code quality standards in their teams.
• Freelancers taking on orders to modify other people's projects.

What will you learn?

After reading, you will be able to confidently refactor any PHP code: from simple scripts to complex frameworks. You will learn to:

• Identify problematic code areas and estimate the effort required to fix them.
• Apply over 30 specific refactoring techniques (Extract Method, Replace Conditional with Polymorphism, Introduce Parameter Object, and others).
• Use static analysis (PHPStan, Psalm) and automated tools (Rector, PHP CS Fixer).
• Build an architecture that easily adapts to new business requirements.

The book contains numerous code examples, practical exercises, and checklists. All examples were tested on PHP 8.2 and are compatible with the latest versions of popular frameworks (Laravel, Symfony).