Persistent PHP objects, inside Cloudflare Durable Objects.

app/Atoms/GameRoom.php

namespace App\Atoms;

use Atoms\Atom;
use Atoms\DatabaseIlluminate\EloquentBridge;
use Atoms\Websocket\Connection;
use Atoms\Websocket\Message;

class GameRoom extends Atom
{
    public function join(string $player): int
    {
        $db = EloquentBridge::boot($this->db());

        $seat = $db->transaction(function () use ($player): int {
            $taken = Player::query()->count();

            if ($taken >= 4) {
                throw new \DomainException('room_full');
            }

            Player::create(['name' => $player, 'seat' => $taken + 1]);

            return $taken + 1;
        });

        $this->broadcast('room', ['kind' => 'joined', 'player' => $player, 'seat' => $seat]);

        return $seat;
    }

    public function onConnect(Connection $conn, array $params): void
    {
        EloquentBridge::boot($this->db());

        Player::where('name', $params['player'])
            ->update(['connection_id' => $conn->id()]);

        $conn->sendJson([
            'kind'  => 'welcome',
            'board' => Piece::all(['piece', 'square', 'owner'])->toArray(),
        ]);
    }

    public function onMessage(Connection $conn, Message $msg): void
    {
        EloquentBridge::boot($this->db());

        $move  = $msg->json();
        $mover = Player::where('connection_id', $conn->id())->first();

        $moved = Piece::where('piece', $move['piece'])
            ->where('owner', $mover?->name)
            ->update(['square' => $move['square']]);

        if ($moved === 1) {
            $this->broadcast('room', ['kind' => 'moved'] + $move);
        }
    }
}

app/Atoms/GameRoom.php

namespace App\Atoms;

use Atoms\Atom;
use Atoms\Database;
use Atoms\Websocket\Connection;
use Atoms\Websocket\Message;

class GameRoom extends Atom
{
    public function join(string $player): int
    {
        $seat = $this->db()->transaction(function (Database $db) use ($player): int {
            $taken = (int) $db->query('SELECT COUNT(*) c FROM players')[0]['c'];

            if ($taken >= 4) {
                throw new \DomainException('room_full');
            }

            $db->execute('INSERT INTO players (name, seat) VALUES (?, ?)', [$player, $taken + 1]);

            return $taken + 1;
        });

        $this->broadcast('room', ['kind' => 'joined', 'player' => $player, 'seat' => $seat]);

        return $seat;
    }

    public function onConnect(Connection $conn, array $params): void
    {
        $this->db()->execute(
            'UPDATE players SET connection_id = ? WHERE name = ?',
            [$conn->id(), $params['player']]
        );

        $conn->sendJson([
            'kind'  => 'welcome',
            'board' => $this->db()->query('SELECT piece, square, owner FROM board'),
        ]);
    }

    public function onMessage(Connection $conn, Message $msg): void
    {
        $move = $msg->json();

        $moved = $this->db()->execute(
            'UPDATE board SET square = ?
              WHERE piece = ?
                AND owner = (SELECT name FROM players WHERE connection_id = ?)',
            [$move['square'], $move['piece'], $conn->id()]
        );

        if ($moved === 1) {
            $this->broadcast('room', ['kind' => 'moved'] + $move);
        }
    }
}