Functional PHP by Crettenand, Gilles -- Read -- Imperial Library of Trantor

Index

Functional PHP

Functional PHP Credits About the Author About the Reviewer www.PacktPub.com

Why subscribe?

Customer Feedback Preface

What this book covers What you need for this book Who this book is for Conventions Reader feedback Customer support

Downloading the example code Errata Piracy Questions

1. Functions as First Class Citizens in PHP

Before we begin

Coding standards Autoloading and Composer

Functions and methods PHP 7 scalar type hints Anonymous functions Closures

Closures inside of classes

Using objects as functions The Closure class Higher-order functions What is a callable? Summary

2. Pure Functions, Referential Transparency, and Immutability

Two sets of input and output Pure functions

What about encapsulation? Spotting side causes Spotting side effects What about object methods? Closing words

Immutability

Why does immutability matter? Data sharing Using constants An RFC is on its way Value objects Libraries for immutable collections

Laravel Collection Immutable.php

Referential transparency

Non-strictness or lazy evaluation

Performance Code readability Infinite lists or streams

Code optimization Memoization

PHP in all that? Summary

3. Functional Basis in PHP

General advice

Making all inputs explicit Avoiding temporary variables Smaller functions Parameter order matters

The map function The filter function The fold or reduce function

The map and filter functions using fold Folding left and right The MapReduce model

Convolution or zip Recursion

Recursion and loops

Exceptions

PHP 7 and exceptions

Alternatives to exceptions

Logging/displaying error message Error codes Default value/null Error handler

The Option/Maybe and Either types

Lifting functions The Either type

Libraries

The functional-php library

How to use the functions General helpers Extending PHP functions Working with predicates Invoking functions Manipulating data Wrapping up

The php-option library Laravel collections

Working with Laravel's Collections

The immutable-php library

Using immutable.php

Other libraries

The Underscore.php library Saber Rawr PHP Functional Functional PHP functional programming Utils Non-standard PHP library

Summary

4. Composing Functions

Composing functions Partial application Currying

Currying functions in PHP

Parameter order matters a lot! Using composition to solve real issues Summary

5. Functors, Applicatives, and Monads

Functors

Identity function Functor laws Identity functor Closing words

Applicative functors

The applicative abstraction Applicative laws

Map Identity Homomorphism Interchange Composition Verifying that the laws hold

Using applicatives

Monoids

Identity law Associativity law Verifying that the laws hold What are monoids useful for? A monoid implementation Our first monoids Using monoids

Monads

Monad laws

Left identity Right identity Associativity Validating our monads

Why monads? Another take on monads A quick monad example

Further reading Summary

6. Real-Life Monads

Monadic helper methods

The filterM method The foldM method Closing words

Maybe and Either monads