AuthenticationService.php

<?php
namespace Project\Services\Authentication;

// This file should reside in your project root's `src\Services` sub-directory

use Illuminate\Hashing\BcryptHasher;
use Psr\Log\LoggerInterface;
use Project\Repositories\UserRepository;

class AuthenticationService {
  private $hasher;
  private $logger;
  private $userRepository;  
  
  public function __construct(BcryptHasher $hasher, LoggerInterface $logger, UserRepository $userRepository)
  {
      $this->hasher = $hasher;
      $this->logger = $logger;
      $this->userRepository = $userRepository;
  }
  
  /**
   * @throws AuthenticationServiceException
   */
  public function authenticate(string $username, string $password, string $ipAddress = null): void
  {
      ... do your authentication logic ...
        
      if ($a === true) {
        throw new AuthenticationServiceException('Message 1');
      } else if ($b === false) {
        throw new AuthenticationServiceException('Message 2');
      }
      
      ... do your logging logic ...
  }
}

AuthenticationServiceException.php

<?php
namespace Project\Services\Authentication;

use Exception;

class AuthenticationServiceException extends Exception
{
}

config.php

<?php

// This file should reside in your project root's `app` sub-directory

return [
    Database::class => DI\factory(function () {
        $dsn = getenv('DB_TYPE') . ':host=' . getenv('DB_HOST') . ';dbname=' . getenv('DB_NAME');
        $db_user = getenv('DB_USERNAME');
        $db_password = getenv('DB_PASSWORD');
        return new Database($dsn, $db_user, $db_password);
    }),

    LoggerInterface::class => DI\factory(function () {
        $loggerApp = new Logger('APP');
        $loggerApp->pushHandler(new RotatingFileHandler(__DIR__ . '/../tmp/logs/app.log', Logger::DEBUG));
        return $loggerApp;
    }),
];

index.php

<?php
use Project\MyApp;
use Project\Actions\RequestAuthenticationAction;

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

$app = new MyApp();

// Middleware
$app->add(new RKA\Middleware\IpAddress(true, ['10.0.0.1', '10.0.0.2']));

// Routes
$app->post('/authentication', RequestAuthenticationAction::class);

$app->run();

MyApp.php

<?php
namespace Project;

// This file should reside in `src` sub-directory of your project

use DI\Bridge\Slim\App;

class MyApp extends App {
    protected function configureContainer(ContainerBuilder $builder)
    {
        $builder->addDefinitions(__DIR__ . '/../app/config.php');
    }
}

RequestAuthenticationAction.php

<?php
namespace Project\Actions;

// This file should reside in your project root's `src\Actions` sub-directory

use Project\Services\Authentication\AuthenticationService;
use Project\Services\Authentication\AuthenticationServiceException;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Rakit\Validation\Validator;

class RequestAuthenticationAction {
  private $authenticationService;
  private $validator;
  
  public function __construct(AuthenticationService $authenticationService, Validator $validator)
  {
      $this->authenticationService = $authenticationService;
      $this->validator = $validator;
  }
  
  public function __invoke(ServerRequestInterface $request, ResponseInterface $response, $args)
  {
      $username = $request->getParsedBodyParam('username', null);
      $password = $request->getParsedBodyparam('password', null);
      $ipAddress = $request->getAttribute('ip_address');
    
      ... do your validation logic with $this->validator ...
        
      try {
        $this->authenticationService->authenticate($username, $password, $ipAddress)
      } catch (AuthenticationServiceException $e) {
        $response->withJson(['error' => $e->getMessage()], 400);
      }
    
      return $response->withJson(['success' => true], 200);
  }
}