Book Image

The Art of Modern PHP 8

By : Joseph Edmonds
5 (1)
Book Image

The Art of Modern PHP 8

5 (1)
By: Joseph Edmonds

Overview of this book

PHP has come a long way since its introduction. While the language has evolved with PHP 8, there are still a lot of websites running on a version of PHP that is no longer supported. If you are a PHP developer working with legacy PHP systems and want to discover the tenants of modern PHP, this is the book for you. The Art of Modern PHP 8 walks you through the latest PHP features and language concepts. The book helps you upgrade your knowledge of PHP programming and practices. Starting with object-oriented programming (OOP) in PHP and related language features, you'll work through modern programming techniques such as inheritance, understand how it contrasts with composition, and finally look at more advanced language features. You'll learn about the MVC pattern by developing your own MVC system and advance to understanding what a DI container does by building a toy DI container. The book gives you an overview of Composer and how to use it to create reusable PHP packages. You’ll also find techniques for deploying these packages to package libraries for other developers to explore. By the end of this PHP book, you'll have equipped yourself with modern server-side programming techniques using the latest versions of PHP.
Table of Contents (19 chapters)
Section 1 – PHP 8 OOP
Free Chapter
Chapter 1: Object-Oriented PHP
Section 2 – PHP Types
Chapter 5: Object Types, Interfaces, and Unions
Section 3 – Clean PHP 8 Patterns and Style
Section 4 – PHP 8 Composer Package Management (and PHP 8.1)
Section 5 – Bonus Section - PHP 8.1

Covariance and contravariance

Covariance and contravariance is one of those topics that once you have got your head around it, then it becomes quite intuitive – however, explaining it is somewhat challenging. The worst thing about covariance and contravariance is the words used to describe them. I admit to always forgetting which one is which!

You can have a look at the Wikipedia page, though you may end up more confused than you were before:

Covariance and contravariance (computer science) - Wikipedia

A much better idea, and, as you have probably gathered, something I generally encourage, is to hit the official PHP docs:

PHP: Covariance and Contravariance - Manual

Covariance and contravariance refer to the rules for what parameter and return types you are allowed to use when extending classes or implementing interfaces.

The following points are quoted from the official docs: