Refactoring PHP Code: Improving Architecture and Performance

The book "Refactoring PHP Code" is a comprehensive practical guide for PHP developers who want to learn how to systematically improve existing code without breaking application functionality. The author, Alexey Sokolov, a senior developer with 10 years of experience, shares proven techniques and strategies that will help transform chaotic "spaghetti code" into an elegant, maintainable, and performant system.

The book is structured from simple to complex and covers all stages of refactoring:

• Refactoring Basics: when and why to refactor, how to assess risks and set priorities.
• "Code Smells": 20+ typical signs of problematic code — from duplication to long methods and god classes.
• Refactoring Catalog: more than 30 specific techniques with examples in PHP 8.x — from simple (extract method, replace magic numbers with constants) to complex (replace inheritance with delegation, refactoring conditional operators).
• Working with Legacy Code: strategies for safe refactoring of inherited systems without tests, "Strangler Fig" and "Sprout Method" techniques.
• Database Refactoring: schema migrations, query optimization, extracting repositories.
• Performance: profiling, loop optimization, caching, memory management.
• Patterns and Architecture: how refactoring leads to proper use of SOLID, Dependency Injection, Strategy, Observer, and other patterns.
• Tools: PHPStan, Rector, PhpStorm, Xdebug, PHPUnit — automation and quality control.

Who is this book for?

• Junior+ and Middle PHP developers looking to improve the quality of their code.
• Team leads and tech leads responsible for project architecture.
• Developers working with legacy code and striving to improve it.
• Anyone who wants to move from "just make it work" to professional development.

What you will learn:

• How to identify and eliminate "code smells" at early stages.
• How to refactor safely using tests and automated tools.
• How to improve application architecture without a full rewrite.
• How to optimize performance without sacrificing readability.
• How to implement best practices from the PHP community (PSR, SOLID, Clean Architecture).

The book contains numerous real-world examples, exercises, and checklists. Each section is accompanied by practical tasks to reinforce the material. This is not just theory — it is a practical guide you can apply tomorrow on your work project.

Suitable for PHP 7.4+ and PHP 8.x. All examples have been tested on current language versions.