phonad/core

Building blocks for functional programming in PHP

v0.1.0 2025-12-18 18:24 UTC

Requires (Dev)

• pestphp/pest: ^4.2
• phpstan/phpstan: ^2.1

MIT

• Christopher Kaster

README

Building blocks for functional programming in PHP, inspired by Haskell.

Note: This is an experiment to play around with Functional Programming in PHP

Install

Install via composer:

$ composer require phonad/core

Data Structures

Maybe

Handles optional values without null.

<?php

use Phonad\Core\Data\Maybe;

$val = Maybe::of(10)
    ->map(fn($n) => $n * 2)
    ->orElse(0); // 20

Either

Error handling: Right for success, Left for failure.

<?php

use Phonad\Core\Data\Either;

$res = Either::Right(10)
    ->flatMap(fn($n) => $n > 5 ? Either::Right($n) : Either::Left("Too small"))
    ->either(fn($err) => "Error: $err", fn($val) => "Value: $val");

ImmutableList

Immutable linked list (PDS).

<?php

use Phonad\Core\Data\ImmutableList;

$list = ImmutableList::from([1, 2, 3])
    ->cons(0)
    ->filter(fn($n) => $n > 0); // [1, 2, 3]

Effects

Reader

Dependency injection via environment.

<?php

use Phonad\Core\Effect\Reader;

$logic = Reader::ask()->map(fn($env) => "Env is: " . $env['mode']);
echo $logic->run(['mode' => 'production']);

Writer

Pure logging alongside values.

<?php

use Phonad\Core\Effect\Writer;

[$val, $logs] = Writer::of(10)
    ->flatMap(fn($n) => Writer::of($n + 1, ["Incremented"]))
    ->run();

IO

Lazy side effects.

<?php

use Phonad\Core\Effect\IO;

// Wrap the effect into the `IO` monad
$sayHello = fn(string $name) => IO::make(function () use ($name) {
    echo "Hello, $name!";
});

// Chain the logic (nothing actually happens yet)
$program = IO::of('world')
    ->map('strtoupper')
    ->flatMap(fn($name) => $sayHello($name));

// FIRE!
$program->run();  // Outputs: Hello, WORLD!

License

MIT