A Command Bus implementation for Mezzio applications, providing a clean way to handle commands through a middleware pipeline.

• CmdBus - The main command bus implementation
• CmdBusInterface - Command bus contract
• MiddlewarePipe - Middleware pipeline management
• MiddlewarePipelineInterface - Pipeline contract
• CommandHandlerFactory - Factory for command handlers
• ConfigProvider - Laminas configuration provider
• Next - Pipeline delegation helper

• CommandInterface - Command contract
• CommandHandlerInterface - Handler contract
• MiddlewareInterface - Middleware contract

• CmdBusFactory - Service factory for CmdBus
• CommandHandlerFactoryFactory - Factory for CommandHandlerFactory
• CommandHandlerMiddlewareFactory - Factory for CommandHandlerMiddleware
• MiddlewarePipeFactory - Factory for MiddlewarePipe

• PreCommandHandlerMiddleware - Middleware for pre-processing commands
• CommandHandlerMiddleware - Final middleware for command execution
• PostCommandHandlerMiddleware - Middleware for post-processing results

• EmptyPipelineHandler - Default handler for empty pipelines

• CommandException - Base command exception
• InvalidConfigurationException - Configuration errors
• NextHandlerAlreadyCalledException - Pipeline state errors
• ServiceNotFoundException - Service resolution errors

composer require php-cmd/cmd-bus

// config/config.php
return [
    PhpCmd\CmdBus\ConfigProvider::class => [
        'command-map' => [
            App\Command\CreateUserCommand::class => App\Handler\CreateUserHandler::class,
        ],
        'middleware_pipeline' => [
            ['middleware' => \PhpCmd\CmdBus\Middleware\CommandHandlerMiddleware::class, 'priority' => 1],
        ],
    ],
];

// In a request handler or middleware
class UserHandler
{
    public function __construct(
        private \PhpCmd\CmdBus\CmdBusInterface $commandBus
    ) {}

    public function handle(ServerRequestInterface $request): ResponseInterface
    {
        $data = $request->getParsedBody();

        $command = new CreateUserCommand(
            email: $data['email'],
            username: $data['username']
        );

        $user = $this->commandBus->handle($command);

        return new JsonResponse(['user' => $user->toArray()]);
    }
}

The cmd-bus library follows these key principles:

1. Commands are data objects that implement CommandInterface
2. Handlers process commands and implement CommandHandlerInterface
3. Middleware can intercept and potentially modify command processing
4. Pipeline manages middleware execution order
5. Factory classes integrate with Laminas ServiceManager/ Psr\Container\ContainerInterface

See the project repository for contribution guidelines and development setup instructions.