The shift towards API driven design has echoed in new design patterns from traditional MVC. Middleware pipelines is geared to address the complexities and nuances that arise with APIs. We'll delve into Expressive, discuss strategies for adding layers, handling authentication and authorization, and implications for projects. Come learn all about middleware and discover how you can leverage pipelines in your development.

1. Stacking Up
Middleware
Mark Niebergall

2. https://upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Iceberg_in_the_Arctic_with_its_underside_exposed.jpg/1280px-Iceberg_in_the_Arctic_with_its_underside_exposed.jpg

3. Objective
• Know how to leverage middleware in your projects
• Familiar with middleware use cases

4. Overview
• What Is Middleware
• Use Cases
• PSR Implementations
• APIs and Middleware
• Automated Testing Considerations
• What Middleware Can Replace

5. What Is Middleware

6. What Is Middleware
https://i.ytimg.com/vi/-FtCTW2rVFM/maxresdefault.jpg

7. Middleware
Middleware
What Is Middleware
Request App Response

8. What Is Middleware
• Inbound request
• Layers of middleware logic
• Ends up in application
• Returns response

9. What Is Middleware
• Connected layers are a processing pipeline
• Request flows through the pipeline
• Output of layer is input to next layer

10. What Is Middleware
• Middleware layer
interface MiddlewareInterface
{
public function process(
ServerRequestInterface $request,
RequestHandlerInterface $handler
): ResponseInterface;
}

11. What Is Middleware
class ApiKeyCheck implements MiddlewareInterface
{
public function process(
ServerRequestInterface $request,
RequestHandlerInterface $handler
): ResponseInterface {
// check for API key
return $handler->handle($request);
}
}

12. What Is Middleware
• Application layer
interface RequestHandlerInterface
{
public function handle(
ServerRequestInterface $request
): ResponseInterface;
}

13. What Is Middleware
class SendEmail implements RequestHandlerInterface
{
public function handle(
ServerRequestInterface $request
): ResponseInterface {
// send an email
return new JsonResponse(
['recipient' => 'abc@example.com']
);
}
}

14. What Is Middleware
• Configuring routes - Laminas, Zend
$app->post(
'/api/change',
[
AppApiChangeGeneratorChangeGeneratorFilter::class,
AppApiChangeGeneratorChangeGeneratorAction::class,
],
'api-change'
);

15. What Is Middleware
• Configuring routes - Laminas, Zend
[
'name' => 'api-change',
'path' => '/api/change',
'middleware' => [
AppApiChangeGeneratorChangeGeneratorFilter::class,
AppApiChangeGeneratorChangeGeneratorAction::class,
],
'allowed_methods' => ['POST'],
],

16. What Is Middleware
• Configuring routes - Slim
$app = new SlimApp();
$app->add(function ($request, $response, $next) {
$response->getBody()->write('BEFORE');
$response = $next($request, $response);
$response->getBody()->write('AFTER');
return $response;
});
$app->get('/', function ($request, $response, $args) {
$response->getBody()->write(' Hello ');
return $response;
});
$app->run();

17. What Is Middleware
• Configuring routes - Laravel
// within AppHttpKernel class
protected $routeMiddleware = [
'auth' => AppHttpMiddlewareAuthenticate::class,
];
Route::get(
'/',
function () {
}
)->middleware('auth', 'another')

18. Use Cases

19. Use Cases
• Authentication
- API key
- User session

20. Use Cases
• Auditing
- Who is requesting what resource

21. Use Cases
• Request filter
- Required data is present
- Format of request data is valid

22. Use Cases
• Exception handling
- Catch exceptions
‣ Route not found
‣ Database is down
‣ Error doing an action

23. Use Cases
• Caching

24. Use Cases
• Rate Limiting

25. Use Cases
• Others?

26. PSR Implementations

27. PSR Implementations
• The PHP Framework Interop Group
• PHP Standards Recommendations

28. PSR Implementations
• PSR-7
- HTTP Message Interfaces
‣ Requests and response
‣ interface MessageInterface {…}
• getProtocolVersion()
• getHeaders()
• hasHeader($name)
• getHeader($name)
• getHeaderLine($name)
• getBody(): StreamInterface
• withX immutable methods

29. PSR Implementations
• PSR-7
- Request
‣ Client-side request
‣ interface RequestInterface extends
MessageInterface
• getRequestTarget()
• getMethod()
• getUri()
• withX immutable methods

30. PSR Implementations
• PSR-7
- Server Request
‣ Server-side request
‣ interface ServerRequestInterface extends
RequestInterface
• getServerParams() (think $_SERVER)
• getCookieParams (think $_COOKIE)
• getQueryParams()
• getUploadedFiles()
• getParsedBody() (array or object)
• getAttributes()
• withX immutable methods

31. PSR Implementations
• PSR-7
- Response
‣ Server-side response
‣ interface ResponseInterface extends
MessageInterface
• getStatusCode() (200, 404, …)
• getReasonPhrase()
• withStatusCode($code, $reasonPhrase = ‘’)
• return new Response(‘Teapot’)
->withStatusCode(418, ‘Tip me over!’);

32. PSR Implementations
• PSR-7
- Streams
- URIs
- Uploaded files

33. PSR Implementations
• PSR-15
- Application handles a request
- Response is returned

34. PSR Implementations
• PSR-15
- HTTP Server Request Handlers
public function handle(
ServerRequestInterface $request
): ResponseInterface;
- Middleware processes a request
public function process(
ServerRequestInterface $request,
RequestHandlerInterface $handler
): ResponseInterface;

35. PSR Implementations
• PSR-17
- HTTP Factories
‣ createRequest(string $method, $uri):
RequestInterface
‣ createResponse(int $code = 200, string
$reasonPhrase = ''): ResponseInterface
‣ createServerRequest(string $method, $uri, array
$serverParams = []): ServerRequestInterface
‣ createStream(string $content = ‘’): StreamInterface
‣ createUploadedFile(…): UploadedFileInterface
‣ createUri(string $uri = ‘’): UriInterface

36. PSR Implementations
• PSR-18
- HTTP Client
‣ interface ClientInterface {…}
‣ sendRequest(RequestInterface $request):
ResponseInterface
- Exceptions
‣ ClientExceptionInterface (unable to send request)
‣ RequestExceptionInterface (request failed)
‣ NetworkExceptionInterface (network problem)

37. PSR Implementations
• Frameworks
- Laminas Mezzio (formerly Zend Expressive)
- Laravel Middleware
‣ Uses Symfony HTTP Foundation Component
- Slim Middleware
- Symphony HTTP Foundation Component
‣ Requests and response
- Others?

38. APIs and Middleware

39. APIs and Middleware
• API requests
• Handling responses

40. APIs and Middleware
• HTTP response codes

41. APIs and Middleware
• Content type

42. APIs and Middleware
• Reusable layers

43. Automated Testing Considerations

44. Automated Testing Considerations
• Ideal is a combination
- Functional tests
- Behavioral tests

45. Automated Testing Considerations
• Functional tests
- PHPUnit
- Test application logic

46. Automated Testing Considerations
• Functional tests
- Test individual middleware layers
- Test application processing
- Test responses being returned from code

47. Automated Testing Considerations
• Behavioral tests
- Behat
- Test responses from requests

48. Automated Testing Considerations
• Behavioral tests
- Tests for middleware layers
- Response codes
- Response information

49. Automated Testing Considerations
• Behavioral tests
- Test authentication
- Test authorization

50. Automated Testing Considerations
• Behavioral tests
- Order of requests made
- Create, read, update, and delete data

51. What Middleware Can Replace

52. What Middleware Can Replace
• Utilities

53. What Middleware Can Replace
• Fat Controller

54. What Middleware Can Replace
• Repetitious services

55. Review
• What Is Middleware
• Use Cases
• PSR Implementations
• APIs and Middleware
• Automated Testing Considerations
• What Can Middleware Replace?

56. Stacking Up Middleware
• Questions?
• https://joind.in/talk/a2e1b

57. Mark Niebergall @mbniebergall
• PHP since 2005
• Masters degree in MIS
• Senior Software Engineer
• Drug screening project
• Utah PHP Co-Organizer
• CSSLP, SSCP Certified and SME
• Father, long distance running, fishing, skiing

58. References
• https://phil.tech/php/2016/05/31/why-care-about-php-
middleware/
• https://blog.ircmaxell.com/2016/05/all-about-
middleware.html
• https://laravel.com/docs/master/middleware
• http://www.slimframework.com/docs/v3/concepts/
middleware.html
• https://github.com/mezzio/mezzio
• https://www.php-fig.org/psr/