Thinking Functionally in PHP
Thinking Functionally in PHP
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Thinking Functionally in PHP

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Completed on 2020-08-21

About the Book

Functional programming has a reputation of being too nerdy, academic, and inscrutable to be useful for "common" programmers. That reputation is only partially unearned, but the concepts behind functional programming are entirely within reach of every programmer in any modern language. That includes PHP. This book takes the reader through the basics of functional programming, the new capabilities of PHP 7.4 that make it even easier, and the computer-science-y underpinnings that make it all possible.

Computer scientists and software engineers tend to speak in entirely different languages, which is part of what makes learning more academic concepts difficult. This book offers both: Practical, applicable examples of how to leverage functional programming, category theory, and even the scary m-word. We start with the very basics and build up slowly, covering both the practical and theoretical just enough to be useful in everyday code.

About the Editor

Larry Garfield
Larry Garfield

Larry Garfield is an aspiring blacksmith who moonlights as Director of Developer Experience for  When not trying to hand-forge his own medieval armory from scratch he tries to teach developers and development managers the skills of yesteryear that the industry has forgotten.

Table of Contents

    • Preface
    • Introduction
      • Functional vs. Procedural
      • Object-Oriented Code
      • Functional Style? Functional Language?
      • Type Systems
      • What to Expect
  • Part One
    • Pure Functions
      • Define “Pure”
      • Composing Functions
      • Binary Functions
    • First Class Functions
      • Anonymous Functions
      • Closure Objects
      • Short Lambdas
      • Object Binding
    • Memoization
    • Currying
    • Mapping
    • Filter
    • Reducing
    • Concatenation
    • Recursion
      • Recursion
    • Immutable Value Objects
      • What PHP Does
      • Making It Immutable
      • Objects, Functionally
      • Evolvable Objects
      • Dependencies
      • Entity Objects
      • Intra-Function Immutability
  • Part Two
    • Category Theory
      • What Is a Category?
      • Objects
      • Some Definitions
      • Structure
      • Let’s Get Meta
      • Isomorphism
      • Monoids
    • Categories in Code
      • Converting Structure
      • Function Objects
    • Fun With Functors
      • Combining Functors
      • Monads in Programming
      • Anatomy of a PHP Monad
    • Algebraic Data Types
      • Products
      • Product Types in PHP
      • Coproducts
      • Coproducts in PHP
  • Part Three
    • Handling Null
      • The Problem
      • The Example
      • The Category Theory Solution
      • The Programming Solution
      • An Alternate Implementation
      • A Note on Types
    • Either/Or and Error Handling
      • The Problem
      • The Example
      • The Category Theory Solution
      • The Programming Solution
      • Either Either?
    • Tracking Data
      • The Problem
      • The Example
      • The Category Theory Solution
      • The Programming Solution
    • Combining Monadic Behavior
      • The Example
      • The General Approach
      • Binding
      • The Lexers
      • Testing
      • Analysis
      • Being Lazy
  • Part Four
    • Features of Functional Languages
      • Auto-Currying
      • Recursion Optimization
      • Isomorphic Optimization
      • Function Composition
      • Function Naming
      • Generics
      • Callable Types
      • Comprehensions
      • Integrated Optionals
      • Optional Chaining
      • A Native Bind Operator
      • Enumerated Types
    • When to Go Functional
      • Avoid Global State
      • Make Pure Functions
      • Isolate IO
      • List Application
      • Embrace Value Objects
      • Embrace Functions as Values
      • Make Single-Method Callable Services
      • Think in Terms of Pipelines and Data Flow
      • Use Maybe and Either for Error Handling
      • Don’t Overdo It
    • Further Resources
      • Books
      • Videos
      • Papers

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