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

## Function composition

The practice of chaining function calls, or **composition,** is common in functional programming. In fact, the spirit of functional programming is composition. A function chain is a nest of functions and, like any series, follows a linear chronology. In a function chain, the output of one function serves as input for the next. This concept is rooted in mathematics, where two functions, $f(x)$ and $g(x)$, can be composed to create a new function, $f(g(x))$, or $f \circ g$.

$$ f(x) = x + 1 $$
$$ g(x) = x^2 $$
$$ f \circ g = x^2 + 1 $$

Function composition in PHP can be approached in one of two ways:
1. Traditional style
2. Point-free style

The first style is quite popular and reflects a composition one may not be aware of at first. The second style enforces more compact function definitions and more recognizable chains.

# Function composition

The practice of chaining function calls, or **composition,** is common in functional programming. In fact, the spirit of functional programming is composition. A function chain is a nest of functions and, like any series, follows a linear chronology. In a function chain, the output of one function serves as input for the next. This concept is rooted in mathematics, where two functions, $f(x)$ and $g(x)$, can be composed to create a new function, $f(g(x))$, or $f \circ g$.

$$ f(x) = x + 1 $$
$$ g(x) = x^2 $$
$$ f \circ g = x^2 + 1 $$

Function composition in PHP can be approached in one of two ways:
1. Traditional style
2. Point-free style

The first style is quite popular and reflects a composition one may not be aware of at first. The second style enforces more compact function definitions and more recognizable chains.

Learn about function composition and its various styles.

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

Function Composition in PHP

Function composition