Uma API JSON num arquivo só.

composer require alencarfreire/stem:^0.3

<?php

declare(strict_types=1);

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

use Stem\App;
use Stem\Request;

$app = new App();

$app->notFound(fn (Request $r) => $r->json(['error' => 'not_found'], 404));

$app->route(function (Request $r): void {
    $r->root(fn () => $r->json(['ok' => true, 'name' => 'StemPHP']));

    $r->on('users', function () use ($r): void {
        $r->get(function () use ($r): void {
            $page = (int) $r->queryParam('page', '1');
            $r->json([
                'page' => $page,
                'data' => [
                    ['id' => 1, 'name' => 'Ada'],
                    ['id' => 2, 'name' => 'Linus'],
                ],
            ]);
        });

        $r->post(function () use ($r): void {
            $body = $r->jsonBody() ?? [];
            $name = $body['name'] ?? '';
            if (!is_string($name) || $name === '') {
                $r->json(['error' => 'name required'], 422);
                return;
            }
            $r->json(['id' => 3, 'name' => $name], 201);
        });

        $r->onInt(function (int $id) use ($r): void {
            $r->on('posts', function () use ($r, $id): void {
                $r->get(fn () => $r->json([
                    'user_id' => $id,
                    'posts' => [['id' => 10, 'title' => 'Hello']],
                ]));
            });

            $r->get(fn () => $r->json(['id' => $id, 'name' => 'Ada']));
            $r->delete(fn () => $r->noContent());
        });
    });
});

$app->run();

php -S localhost:8080 index.php

curl -s localhost:8080/users/1
# 200  {"id":1,"name":"Ada"}

curl -s localhost:8080/users/1/posts
# 200  {"user_id":1,"posts":[{"id":10,"title":"Hello"}]}

curl -s -o /dev/null -w '%{http_code}\n' -X DELETE localhost:8080/users/1
# 204

curl -s localhost:8080/nope
# 404  {"error":"not_found"}

curl -s -o /dev/null -w '%{http_code}\n' -X PUT localhost:8080/users
# 405  Allow: GET, HEAD, POST

examples/app/
  index.php                 # router do php -S
  worker.php                # FrankenPHP: AppFactory::make() fora do loop
  AppFactory.php            # PDO + App + $r->run(...)
  Database.php              # sqlite em arquivo, ou qualquer DSN
  schema.sql
  Repository/UserRepository.php
  routes/users.php          # Closure(Request): void
  var/app.sqlite            # criado em runtime

php -S localhost:8080 examples/app/index.php
curl -s localhost:8080/users
curl -s -X POST localhost:8080/users \
  -H 'Content-Type: application/json' -d '{"name":"Grace"}'

$pdo ??= Database::connect();
$users = new UserRepository($pdo);
$makeUsers = require __DIR__ . '/routes/users.php';
$app->route(function (Request $r) use ($makeUsers, $users): void {
    $r->run($makeUsers($users));
});

public function find(int $id): ?array
{
    $st = $this->pdo->prepare('SELECT id, name FROM users WHERE id = :id');
    $st->execute(['id' => $id]);
    $row = $st->fetch();

    return $row === false ? null : /* map */;
}

$r->onInt(function (int $id) use ($r, $users): void {
    $user = $users->find($id);
    if ($user === null) {
        $r->json(['error' => 'not_found'], 404);
        return;
    }
    $r->get(fn () => $r->json($user));
    $r->delete(function () use ($r, $users, $id): void {
        $users->delete($id);
        $r->noContent();
    });
});

$r->on('users', function () use ($r): void {
    $r->post(function () use ($r): void {
        $body = $r->jsonBody() ?? [];
        $name = $body['name'] ?? '';
        if (!is_string($name) || $name === '') {
            $r->json(['error' => 'name required'], 422);
            return;
        }
        $r->json(['id' => 3, 'name' => $name], 201);
    });
});

$r->on('admin', function () use ($r): void {
    if ($r->bearerToken() !== 'secret') {
        $r->json(['error' => 'unauthorized'], 401);
        return;
    }

    $r->get(fn () => $r->json(['ok' => true]));
    $r->post(fn () => $r->json(['queued' => true], 202));
});

$r->on('users', function () use ($r): void {
    $r->onInt(function (int $id) use ($r): void {
        $r->on('posts', function () use ($r, $id): void {
            $r->get(fn () => $r->json(['user_id' => $id, 'posts' => []]));
        });

        $r->get(fn () => $r->json(['id' => $id]));
        $r->delete(fn () => $r->noContent());
    });
});

// routes/users.php
return function (Request $r): void {
    $r->on('users', function () use ($r): void {
        $r->get(fn () => $r->json([['id' => 1]]));
    });
};

// index.php
$app->route(function (Request $r): void {
    $r->run(require __DIR__ . '/routes/users.php');
    $r->run(require __DIR__ . '/routes/posts.php');
});

$app->notFound(fn (Request $r) => $r->json([
    'error' => 'not_found',
    'path' => $r->path(),
], 404));

$app->error(function (Throwable $e, Request $r): void {
    $r->json(['error' => 'server_error', 'detail' => $e->getMessage()], 500);
});

$response = $app->handle(Request::create(
    'POST',
    '/users',
    ['Content-Type' => 'application/json'],
    [],
    '{"name":"Grace"}',
));

assert($response->status() === 201);
assert($response->body() === '{"id":3,"name":"Grace"}');

$r->on('users', function () use ($r): void {
    $r->isInt(function (int $id) use ($r): void {
        $r->get(fn () => $r->json(['id' => $id]));
    });
});

$r->json(['ok' => true], 200);
$r->html('<h1>Oi</h1>');
$r->redirect('/users', 302);
$r->noContent();
$r->cookie('sid', 'abc', ['path' => '/', 'httponly' => true, 'samesite' => 'Lax']);

$app->route(function (Request $r): void { /* uma vez */ });
$response = $app->handle($request);   // por request
$app->run();                          // fromGlobals + handle + send

use Stem\Integrations\FrankenPhpWorker;

FrankenPhpWorker::run(
    $app,
    maxRequests: (int) ($_SERVER['MAX_REQUESTS'] ?? 0),
    collectEvery: 0,
);

$r->root(fn () => $r->json(['ok' => true]));
$r->branches([
    'users' => $makeUsers($users),
    'customers' => $makeCustomers($customers),
]);

php -S 127.0.0.1:8080 index.php
wrk -t4 -c20 -d10s --latency http://127.0.0.1:8080/customers