Gain insights into functional programming in PHP. Learn about pure functions, immutable data, and monads. Explore error handling and apply principles through practical projects.

fp15aug.tar.gz

php7.4

ch8-phonebook

php8.1

purescript

python-pytoolz

chapter5-challenge1

AMQP

eris-testing-lesson

AMQP-Challenge

eris-testing-challenge

Functional programming is a paradigm that emphasizes expressing program logic as compositions of pure functions. PHP is a good fit for functional programming as functions are first-class citizens in its userland.
 
This course introduces you to the core concepts of functional programming, like pure functions, immutable data structures, and referential transparency. From there, you'll explore ways to handle errors with default values and callbacks while also exploring sum types such as Either or Maybe. Next, you'll look at functors before diving deep into monads, including IO, State, Reader, and List.
 
By the end of this course, you'll have a keen understanding of how to apply these principles in practice through a worked-out project. Not only will you know another way to program, but you’ll also feel confident enough to apply these ideas to your projects in PHP.

Learn Functional Programming in PHP

# Overview

A **referentially transparent** function is one in which the function call is interchangeable with the output of the function. This interchangeability shouldn’t affect a program’s side effects or side causes. Like immutability, referential transparency is associable with pure functions. In fact, the latter is a metric for measuring the former.


<?php

$insertUnderscores = fn (string $text): string => ( 
    implode('_', explode(' ', $text))
);
var_dump($insertUnderscores('hello world') === 'hello_world');  // evaluates to true

The lambda function above replaces spaces in a text with underscores. This function’s output, with a `"hello world"` input, is compared with the underscore-separated string `"hello_world"`. The comparison yields a positive result, implying that this function call could’ve been replaced with the string, `"hello_world"`, without changing the code’s semantics.

# Referential transparency with higher-order functions

Not only does referential transparency highlight the usefulness of functional programming, but it also encourages the use of higher-order functions and lazy evaluation. Higher-order functions can exist throughout a program and provide state transformation premised on function usage as either input or output. The same `insertUnderscores` lambda function can appear as follows:

Learn about referentially transparent functions with different useful examples.


Referential Transparency

Learn about referentially transparent functions with different useful examples.

Getting Started

An Introduction to Functional Programming in PHP

Core Concepts: Functional Programming in PHP

Composition and Helper Functions

Error Handling in Functional Programming

Functors in PHP

Parallelization of Tasks in PHP

Recursion, Pattern Matching, and Property Testing

Phonebook Application — A Simple Project

Conclusion

Appendix

Referential Transparency

Overview