index.php

<?php
declare(strict_types=1);

use App\Application\Handlers\HttpErrorHandler;
use App\Application\Handlers\ShutdownHandler;
use App\Application\ResponseEmitter\ResponseEmitter;
use DI\ContainerBuilder;
use Slim\Factory\AppFactory;
use Slim\Factory\ServerRequestCreatorFactory;

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

// Instantiate PHP-DI ContainerBuilder
$containerBuilder = new ContainerBuilder();

if (false) { // Should be set to true in production
	$containerBuilder->enableCompilation(__DIR__ . '/../var/cache');
}

// Set up settings
$settings = require __DIR__ . '/../app/settings.php';
$settings($containerBuilder);

// Set up dependencies
$dependencies = require __DIR__ . '/../app/dependencies.php';
$dependencies($containerBuilder);

// Set up repositories
$repositories = require __DIR__ . '/../app/repositories.php';
$repositories($containerBuilder);

// Build PHP-DI Container instance
$container = $containerBuilder->build();

// Instantiate the app
AppFactory::setContainer($container);
$app = AppFactory::create();
$callableResolver = $app->getCallableResolver();

// Register middleware
$middleware = require __DIR__ . '/../app/middleware.php';
$middleware($app);

// Register routes
$routes = require __DIR__ . '/../app/routes.php';
$routes($app);

/** @var bool $displayErrorDetails */
$displayErrorDetails = $container->get('settings')['displayErrorDetails'];

// Create Error Handler
$responseFactory = $app->getResponseFactory();
$errorHandler = new HttpErrorHandler($callableResolver, $responseFactory);

// Create Shutdown Handler
$shutdownHandler = new ShutdownHandler(null, $errorHandler, $displayErrorDetails);
register_shutdown_function($shutdownHandler);

// Create Request object from globals
$serverRequestCreator = ServerRequestCreatorFactory::create();
$request = $serverRequestCreator->createServerRequestFromGlobals();

// Set Request Object On Shutdown Handler
$shutdownHandler->setRequest($request);

// Add Routing Middleware
$app->addRoutingMiddleware();

// Add Error Middleware
$errorMiddleware = $app->addErrorMiddleware($displayErrorDetails, false, false);
$errorMiddleware->setDefaultErrorHandler($errorHandler);

// Run App & Emit Response
$response = $app->handle($request);
$responseEmitter = new ResponseEmitter();
$responseEmitter->emit($response);

ShutdownHandler.php

<?php
declare(strict_types = 1);

use Psr\Http\Message\ServerRequestInterface;
use Slim\Exception\HttpInternalServerErrorException;
use Slim\ResponseEmitter;

class ShutdownHandler
{
    private ServerRequestInterface $request = null;

    private HttpErrorHandler $errorHandler;

    private bool $displayErrorDetails;

    /**
     * @param ServerRequestInterface $request
     * @param                        $errorHandler $errorHandler
     * @param bool                   $displayErrorDetails
     */
    public function __construct(
        ServerRequestInterface $request = null,
        HttpErrorHandler $errorHandler,
        bool $displayErrorDetails
    ) {
        $this->request = $request;
        $this->errorHandler = $errorHandler;
        $this->displayErrorDetails = $displayErrorDetails;
    }
  
    public function setRequest(ServerRequestInterface $request): void
    {
      $this->request = $request;
    }

    public function __invoke()
    {
        $error = error_get_last();
        if ($error) {
            $errorFile = $error['file'];
            $errorLine = $error['line'];
            $errorMessage = $error['message'];
            $errorType = $error['type'];
            $message = 'An error while processing your request. Please try again later.';

            if ($this->displayErrorDetails) {
                switch ($errorType) {
                    case E_USER_ERROR:
                        $message = "FATAL ERROR: {$errorMessage}. ";
                        $message .= " on line {$errorLine} in file {$errorFile}.";
                        break;

                    case E_USER_WARNING:
                        $message = "WARNING: {$errorMessage}";
                        break;

                    case E_USER_NOTICE:
                        $message = "NOTICE: {$errorMessage}";
                        break;

                    default:
                        $message = "ERROR: {$errorMessage}";
                        $message .= " on line {$errorLine} in file {$errorFile}.";
                        break;
                }
            }

            $exception = new HttpInternalServerErrorException($this->request, $message);
            $response = $this->errorHandler->__invoke($this->request, $exception, $this->displayErrorDetails, false, false);

            $responseEmitter = new ResponseEmitter();
            $responseEmitter->emit($response);
        }
    }
}