README

A functional HTTP library for PHP inspired by Scala's http4s.

Overview

Http4p provides a purely functional approach to building HTTP servers and clients in PHP. Built on Phunkie Effect and Streams, it offers:

Routes as values - GET, POST and friends build a list of routes, the router matches the path
Effect-based handlers - Every handler returns IO<Response>, nothing runs until the server runs it
Bodies decoded against your classes - decode($req, User::class) validates the JSON body against the constructor and answers a bad body with a 400 listing every problem
Streaming bodies - Responses use Stream for constant memory usage
Composable middleware - Through($app, Logger(), Cors(), Recover(...))
Errors answered where you decide - Recover(SomeException::class, $handler) turns an exception into a response for the whole app, IO::recover() for one route

Installation

composer require phunkie/http4p

Requirements

PHP 8.2 || 8.3 || 8.4 || 8.5
phunkie/phunkie ^1.5
phunkie/effect ^1.4
phunkie/streams ^1.2

Core Concepts

Response Model

Http4p uses Response where the body is a Stream:

class Response {
    public Status $status;
    public Headers $headers;
    public Stream $body;  // Stream
}

This design enables:

Constant memory - Stream large responses without loading into memory
Backpressure - Handle slow clients gracefully
Cancellation - Stop processing when client disconnects
Composable effects - Body production can perform IO operations

Type Signatures

Route handlers return IO:

// Handler signature
// fn(int $id): IO<Response>
fn(int $id): IO;

// Response constructors return IO<Response>
Ok($value);        // EntityEncoder turns the value into a JSON body
Ok($stream);       // Uses the stream as the body

The constructors take the body as their first argument, so they compose as first-class callables: $io->flatMap(Ok(...)).

Quick Start

<?php

use Phunkie\Http4p\Request;
use Phunkie\Http4p\Router;
use Phunkie\Http4p\Server\PhpServer;

use function Phunkie\Http4p\Functions\decode;
use function Phunkie\Http4p\Functions\HttpRoutes;
use function Phunkie\Http4p\Functions\middleware\{Recover, Through};
use function Phunkie\Http4p\Functions\response\{Created, NotFound, Ok};
use function Phunkie\Http4p\Functions\routes\{GET, POST};

require_once __DIR__ . '/vendor/autoload.php';

final readonly class User
{
    public function __construct(public string $name, public string $email) {}
}

$users = new Users();   // whatever holds your data; its methods return IO

$app = Through(
    new Router(HttpRoutes(
        GET('/users', fn() => $users->all()->flatMap(Ok(...))),

        GET('/users/:id', fn(int $id) => $users->get($id)->flatMap(Ok(...))),

        POST('/users', fn(Request $req) =>
            decode($req, User::class)
                ->flatMap(fn(array $data) => $users->add($data))
                ->flatMap(Created(...))
        ),
    )),
    Recover(UserNotFound::class, fn(UserNotFound $e) => NotFound(['error' => $e->getMessage()])),
);

(new PhpServer($app))->run(8080)->unsafeRun();

A POST /users with {"name": 7} never reaches the handler; the router answers:

{"error": "Body does not describe User.", "errors": {"name": "expected string, got int", "email": "missing"}}

Calling another service

send is the client: a Request in, an IO<Response> out, its body a stream read from the connection as it is compiled. A newline-delimited JSON export decodes straight into entities, one line at a time:

use function Phunkie\Http4p\Functions\client\send;
use function Phunkie\Http4p\Functions\decodeLines;

send(Request(Method::GET, 'http://catalogue.internal/books/export'))
    ->flatMap(fn(Response $response) => decodeLines($response, Book::class)
        ->evalTap(fn(Book $book) => io(fn() => $index->add($book)))
        ->compile()
        ->drain())
    ->unsafeRun();

The server writes and flushes each chunk before producing the next, and the client reads the same way, so neither side holds more than a chunk of the export. See Client and Streaming.

Documentation

Full documentation is available in docs/.

License

MIT Licence

Acknowledgments

Inspired by http4s
Built on Phunkie

phunkie / http4p

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