Functional Programming in PHP
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Functional Programming in PHP

About the Book

Functional Programming, a style predicated on the Lambda Calculus, is one of the more prominent trends in engineering today. For many, the style's verbiage is dishearteningly esoteric despite the salience of its many ideas in various codebases. PHP remains one of the most used languages for web development and has taken several leaps and bounds since its inception in the twentieth century - advancements that have rendered the language functional programming-amiable. 

The book, Functional Programming in PHP, is an attempt to distill paradigm-centric ideas for PHP audiences - its purpose is to make sense of the abstruseness. 

About the Author

Lochemem Bruno Michael
Lochemem Bruno Michael

PHP and Functional Programming enthusiast; podcaster and content creator.

About the Contributors

Cees-Jan Kiewiet
Cees-Jan Kiewiet


Mr. Cees-Jan Kiewiet is a Senior engineer at Usabilla and core maintainer of ReactPHP. Based in the Netherlands, he has over fifteen years of programming experience and is proficient in, besides PHP, Golang, and Java. Mr. Kiewiet loves to play video games, meet with developers at meetups, and bask in the tranquility of his garden when he is not breaking servers

Chun-Sheng Li
Chun-Sheng Li


Chun-Sheng, Li is a web backend developer from Taiwan, Taipei.

He is currently based in Hsinchu. Mr. Chun-Sheng is familiar with PHP and JavaScript. He loves to develop web applications, web services and some open source projects on Github.

In addition to PHP, He also loves to research other technologies. Like JavaScript, web security, Blockchain, and IOTA. He’s also a backend developer and works in Industrial Technology Research Institute. Mr.Chun-Sheng is a blog writer, open source project contributor and traveler.

Table of Contents

  • Introduction to Functional Programming in PHP  
    • A brief history of PHP
    • A Brief History of Functional Programming
    • Defining Functional Programming
    • Functional Programming is a Declarative Paradigm
    • The Benefits of Functional Programming
    • Relevance to a PHP Developer
    • Functional Programming in Other Contexts
  • Functional Programming Core Concepts  
    • Functions
    • Functional Programming and Object-Oriented Programming
    • Pure Functions
    • Side-causes and side-effects
    • Dealing with side-effects and side-causes
    • A Brief Note About Type Signatures
    • Immutability
    • Constants in PHP
    • Immutable lists
    • Tries
    • Value Objects
    • Temporal Coupling
    • Transient Mutation
    • Referential Transparency
    • REPL Environments for Functional Programming
  • Composition and Helper Functions
    • Composing Functions
    • Traditional Function Composition
    • Point-free Function Composition
    • Currying
    • Partial Application
    • Map, Filter, and Fold
    • Transducers
    • Helper Functions
  • Error Handling in Functional Programming
    • Exceptions are Impure
    • Working Without Exceptions
    • Callbacks
    • PHP Error Messages
    • Default Values
    • Sum and Union Types
    • The Maybe Monad
    • The Either Monad
    • The Railway Pattern
  • Functors
    • A Crashcourse in Category Theory
    • Defining Category Theory
    • What About Functors
    • Functors in Programming
    • Functors are Type Classes
    • Functor Properties
    • Monads
    • Practical Monads
    • Monad Functions
    • The IO Monad
    • The Reader Monad
    • The State Monad
    • The Writer Monad
    • The List Monad
  • Parallelization of Tasks in PHP
    • PHP's Capabilities
    • Threading in PHP
    • The pthreads extension
    • parallel is a Better Threading Option
    • Multiprocessing in PHP
    • Message Brokers
  • Recursion, Pattern Matching and Property Testing
    • Recursion
    • Pattern Matching
    • Property Testing
  • A Simple Project
  • Appendix

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