Von Chaos zu Kontrolle Exception Handling in Symfony SymfonyLive Berlin 2023 

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Anne-Julia Seitz Softwareentwicklerin 15 Jahre PHP Symfony seit v1.2 seit 2021 bei QOSSMIC Organisatorin der Symfony User Group Berlin 

Workshops & Training für Symfony & React User Groups & Community Events Unterstützung von Teams in Symfony- Projekten 

Was erwartet euch 1. Exceptions in PHP 2. Exception Handling in Symfony 3. Antipatterns 4. Best Practices 

Exceptions in PHP 

Hello World! Hello, World!



Exceptions vor PHP 5 /* intentional Error */ $file = @file('not-existing-file.csv') or die("File could not be opened: Error:'" . error_get_las 1 2 3 

set_error_handler() Output: function handleError(int $code, string $description, strin echo "Error: [$code] $description - $file:$line"; return true; } // Switch to custom error handling $previousHandler = set_error_handler("handleError"); // Trigger an error to test the custom error handler echo $undefinedVariable; // Restore previous error handler restore_error_handler(); 1 2 3 4 5 6 7 8 9 10 11 12 13 Error: [2] Undefined variable $undefinedVariable - /in/5YJdO: 

trigger_error() if ($divisor == 0) { trigger_error("Cannot divide by zero.", E_USER_ERROR); } 1 2 3 

Exceptions ab PHP 5 try { throw new \InvalidArgumentException('Variable must be n } catch (\InvalidArgumentException $exception) { // handle exception } finally { // clean up resources } 1 2 3 4 5 6 7 

SPL Exceptions Throwable ├── Error │ └── ... └── Exception ├── LogicException │ ├── BadFunctionCallException │ │ └── BadMethodCallException │ ├── DomainException │ ├── InvalidArgumentException │ ├── LengthException │ └── OutOfRangeException └── RuntimeException ├── OutOfBoundsException ├── OverflowException ├── RangeException ├── UnderflowException └── UnexpectedValueException 

Eigene Exceptions namespace App\Exception; class CategoryAlreadyExists extends \RuntimeException {} 1 2 3 throw new CategoryAlreadyExists('The category you chose alr 1 

set_error_handler vs. try-catch 

ExceptionHandling in Symfony 

public/index.php $kernel = new Kernel($_SERVER['APP_ENV'], (bool) $_SERVER[' $request = Request::createFromGlobals(); $response = $kernel->handle($request); $response->send(); $kernel->terminate($request, $response); 1 2 3 4 5 $response = $kernel->handle($request); $kernel = new Kernel($_SERVER['APP_ENV'], (bool) $_SERVER[' 1 $request = Request::createFromGlobals(); 2 3 $response->send(); 4 $kernel->terminate($request, $response); 5 

Was passiert im Kernel? $kernel->handle($request) ➜ boot() ➜ foreach ($this->getBundles() as $bundle) ➜ $bundle->boot() // \Symfony\Bundle\FrameworkB ➜ ErrorHandler::register() ➜ set_error_handler([$handler, 'handl 1 2 3 4 5 6 $kernel->handle($request) ➜ boot() 1 2 ➜ foreach ($this->getBundles() as $bundle) 3 ➜ $bundle->boot() // \Symfony\Bundle\FrameworkB 4 ➜ ErrorHandler::register() 5 ➜ set_error_handler([$handler, 'handl 6 ➜ foreach ($this->getBundles() as $bundle) $kernel->handle($request) 1 ➜ boot() 2 3 ➜ $bundle->boot() // \Symfony\Bundle\FrameworkB 4 ➜ ErrorHandler::register() 5 ➜ set_error_handler([$handler, 'handl 6 ➜ $bundle->boot() // \Symfony\Bundle\FrameworkB $kernel->handle($request) 1 ➜ boot() 2 ➜ foreach ($this->getBundles() as $bundle) 3 4 ➜ ErrorHandler::register() 5 ➜ set_error_handler([$handler, 'handl 6 ➜ ErrorHandler::register() ➜ set_error_handler([$handler, 'handl $kernel->handle($request) 1 ➜ boot() 2 ➜ foreach ($this->getBundles() as $bundle) 3 ➜ $bundle->boot() // \Symfony\Bundle\FrameworkB 4 5 6 

ErrorHandler Component // Symfony\Component\ErrorHandler\ErrorHandler public static function register(self $handler = null, bool { } 1 2 3 if (null === self::$reservedMemory) { 4 self::$reservedMemory = str_repeat('x', 32768); 5 } 6 7 set_error_handler([$handler, 'handleError']) 8 9 if (null === self::$reservedMemory) { self::$reservedMemory = str_repeat('x', 32768); } // Symfony\Component\ErrorHandler\ErrorHandler 1 public static function register(self $handler = null, bool 2 { 3 4 5 6 7 set_error_handler([$handler, 'handleError']) 8 } 9 

ErrorHandler->handleError() // Symfony\Component\ErrorHandler\ErrorHandler public function handleError(int $type, string $message, str { // ... $logMessage = $this->levels[$type].': '.$message; throw new \ErrorException($logMessage, 0, $type, $file, } 1 2 3 4 5 6 7 throw new \ErrorException($logMessage, 0, $type, $file, // Symfony\Component\ErrorHandler\ErrorHandler 1 public function handleError(int $type, string $message, str 2 { 3 // ... 4 $logMessage = $this->levels[$type].': '.$message; 5 6 } 7 

HttpKernel->handle() // Symfony\Component\HttpKernel\HttpKernel public function handle(Request $request, int $type = self: { try { return $this->handleRaw($request, $type); } catch (\Throwable $e) { return $this->handleThrowable($e, $request, $type) } } private function handleThrowable(\Throwable $e, Request $r { $event = new ExceptionEvent($this, $request, $type, $e $this->dispatcher->dispatch($event, KernelEvents::EXCE return $event->getResponse(); } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 return $this->handleThrowable($e, $request, $type) $this->dispatcher->dispatch($event, KernelEvents::EXCE // Symfony\Component\HttpKernel\HttpKernel 1 public function handle(Request $request, int $type = self: 2 { 3 try { 4 return $this->handleRaw($request, $type); 5 } catch (\Throwable $e) { 6 7 } 8 } 9 10 private function handleThrowable(\Throwable $e, Request $r 11 { 12 $event = new ExceptionEvent($this, $request, $type, $e 13 14 return $event->getResponse(); 15 } 16 

@throws 

Recap Symfony behandelt alle Fehler als Exceptions HttpKernel dispatched ein kernel.exception Event 

Antipatterns 

Return Booleans function divide($numerator, $denominator): float|false { if ($denominator == 0) { return false; } else { return $numerator / $denominator; } } $result = divide(10, 0); if ($result === false) { echo "Error: Division by zero is not allowed."; } else { echo "Result: " . $result; } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 

ExceptionHandling dominiert die Codebasis final class ShowArticleController { #[Route("/articles/{articleId}", name="blog_article_show")] public function __invoke(int $articleId, ArticleRepository { try { $article = $articleRepository->find($articleId); return new JsonResponse(['article' => $article]); } catch (ArticleNotFoundException $e) { return new JsonResponse(['error' => $e->errorMessage()] } catch (ArticleExpiredException $e) { return new JsonResponse(['error' => $e->getMessage()], } catch (\Exception $e) { return new JsonResponse(['error' => $e->getMessage()], } } } 

Return null // CreateArticleCommandHandler public function handle(CreateArticleCommand $command): ?Ar { try { $article = new Article($command->title, $command-> $this->articleRepository->save($article); return $article; } catch (ArticleAlreadyExistsException $exception) { return null; } } // CreateArticleController public function __invoke(CreateArticleCommand $command): R { $articleCreated = $this->handler->handle($command); if (null === $articleCreated) { throw new HttpException(500, 'Could not create art } return new JsonResponse($orderCreated); } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 return null; if (null === $articleCreated) { throw new HttpException(500, 'Could not create art } // CreateArticleCommandHandler 1 public function handle(CreateArticleCommand $command): ?Ar 2 { 3 try { 4 $article = new Article($command->title, $command-> 5 $this->articleRepository->save($article); 6 return $article; 7 } catch (ArticleAlreadyExistsException $exception) { 8 9 } 10 } 11 // CreateArticleController 12 public function __invoke(CreateArticleCommand $command): R 13 { 14 $articleCreated = $this->handler->handle($command); 15 16 17 18 return new JsonResponse($orderCreated); 19 } 20 

Unterdrückte Exceptions try { $this->doSomethingThrowingAnException(); } catch (\Exception $exception) {} 1 2 3 4 try { 5 // ... 6 } catch (\Exception $exception) { 7 throw new \RuntimeException('Something bad happened.') 8 } 9 10 try { 11 // ... 12 } catch (\Exception $exception) { 13 throw new \RuntimeException('Something bad happened.', 14 } 15 try { // ... } catch (\Exception $exception) { throw new \RuntimeException('Something bad happened.') } try { 1 $this->doSomethingThrowingAnException(); 2 } catch (\Exception $exception) {} 3 4 5 6 7 8 9 10 try { 11 // ... 12 } catch (\Exception $exception) { 13 throw new \RuntimeException('Something bad happened.', 14 } 15 try { // ... } catch (\Exception $exception) { throw new \RuntimeException('Something bad happened.', } try { 1 $this->doSomethingThrowingAnException(); 2 } catch (\Exception $exception) {} 3 4 try { 5 // ... 6 } catch (\Exception $exception) { 7 throw new \RuntimeException('Something bad happened.') 8 } 9 10 11 12 13 14 15 

Exceptions als Kontrollstruktur verwenden try { $this->receiveMoneyFromUser(User $user, Money $money); } catch (\PaymentException $exception) { if ($exception instanceof SuccessfulPaymentException) $this->sendEmailToUser($user, 'Thank you for your } elseif ($exception instanceof FailedPaymentException $this->sendEmailToAdmin('Payment failed: ' . $exce } else { $this->sendEmailToAdmin('Something failed: ' . $ex } } 1 2 3 4 5 6 7 8 9 10 11 if ($exception instanceof SuccessfulPaymentException) } elseif ($exception instanceof FailedPaymentException try { 1 $this->receiveMoneyFromUser(User $user, Money $money); 2 } catch (\PaymentException $exception) { 3 4 $this->sendEmailToUser($user, 'Thank you for your 5 6 $this->sendEmailToAdmin('Payment failed: ' . $exce 7 } else { 8 $this->sendEmailToAdmin('Something failed: ' . $ex 9 } 10 } 11 

Broad Catching try { $this->doSomethingThrowingAnException(); } catch (\Exception $exception) { // ... } 1 2 3 4 5 

AppException to rule them all try { throw new AppException('Sorry something went wrong.'); } catch (AppException $exception) { if (str_contains($exception->getMessage(), 'Article not f return new Response($exception->getMessage(), Respons } return new Response($exception->getMessage(), Response::H } 1 2 3 4 5 6 7 8 

Verwendung der HttpExceptions namespace Symfony\Component\HttpKernel\Exception; HttpException ├── AccessDeniedHttpException ├── BadRequestHttpException ├── ConflictHttpException ├── GoneHttpException ├── LengthRequiredHttpException ├── MethodNotAllowedHttpException ├── NotAcceptableHttpException ├── NotFoundHttpException ├── PreconditionFailedHttpException ├── PreconditionRequiredHttpException ├── ServiceUnavailableHttpException ├── TooManyRequestsHttpException ├── UnauthorizedHttpException └── UnsupportedMediaTypeHttpException 

Ad-hoc Error Handling final class CreateArticleController { public function __invoke(Request $request): Response { try { // ... } catch (\Exception $exception) { return $this->json(['message' => $exception->getM } } } 

Best Practices 

Eigenes ExceptionInterface namespace App\Exception; interface ExceptionInterface extends \Throwable { } 1 2 3 4 5 

SPL Exceptions erweitern namespace App\Exception; class ArticleNotFoundException extends \RuntimeException im { } 1 2 3 4 5 Throwable └── Exception ├── LogicException │ ├── Symfony\Component\Console\Exception\LogicExcep │ └── Symfony\Component\ExpressionLanguage\SyntaxErr └── RuntimeException ├── App\Exception\ArticleNotFoundException └── Symfony\Component\Filesystem\Exception\Runtim 

Mögliche Granularität des ExceptionHandlings 

1. Alle Exceptions try { throw new \App\Exception\ArticleNotFoundException(); } catch (\Exception $exception) ( // ... ) 1 2 3 4 5 } catch (\Exception $exception) ( try { 1 throw new \App\Exception\ArticleNotFoundException(); 2 3 // ... 4 ) 5 

2. Alle unsere Exceptions try { throw new \App\Exception\ArticleNotFoundException(); } catch( \App\Exception\ExceptionInterface $exception ) ( // ... ) 1 2 3 4 5 } catch( \App\Exception\ExceptionInterface $exception ) ( try { 1 throw new \App\Exception\ArticleNotFoundException(); 2 3 // ... 4 ) 5 

3. Spezifische SPL Exception try { throw new \App\Exception\ArticleNotFoundException(); } catch( \RuntimeException $exception ) ( // ... ) 1 2 3 4 5 } catch( \RuntimeException $exception ) ( try { 1 throw new \App\Exception\ArticleNotFoundException(); 2 3 // ... 4 ) 5 

4. Erweiterte SPL exception von der App try { throw new \App\Exception\ArticleNotFoundException(); } catch( \App\Exception\ArticleNotFoundException $exceptio // ... ) 1 2 3 4 5 } catch( \App\Exception\ArticleNotFoundException $exceptio try { 1 throw new \App\Exception\ArticleNotFoundException(); 2 3 // ... 4 ) 5 

Static Factory Methods namespace App\Exception; class ArticleNotFoundException extends \RuntimeException i { public static function create(): self { return new self('Article was not found.'); } public static function createWithArticleTitle(string $ { return new self(sprintf('Article "%s" was not foun } } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 throw ArticleNotFoundException::createWithArticleTitle('errar 

Wir erstellen einen ExceptionListener #[AsEventListener(event: KernelEvents::EXCEPTION, priority final class ExceptionListener { public function __invoke(ExceptionEvent $event): void { $exception = $event->getThrowable(); $response = match (true) { $exception instanceof HttpExceptionInterface => new Response($exception->getMessage(), $exception- default => new Response('Internal Server Error', Response::HT }; $event->setResponse($response); } } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 $exception instanceof HttpExceptionInterface => new Response($exception->getMessage(), $exception- default => new Response('Internal Server Error', Response::HT #[AsEventListener(event: KernelEvents::EXCEPTION, priority 1 final class ExceptionListener 2 { 3 public function __invoke(ExceptionEvent $event): void 4 { 5 $exception = $event->getThrowable(); 6 $response = match (true) { 7 8 9 10 11 }; 12 $event->setResponse($response); 13 } 14 } 15 

public function __invoke(ExceptionEvent $event): void { $exception = $event->getThrowable(); $response = match (true) { $exception instanceof HttpExceptionInterface => new Response($exception->getMessage(), $exception->g $exception instanceof ExceptionInterface => new Response($exception->getMessage(), $this->mapExc default => new Response('Internal Server Error', Respo }; $event->setResponse($response); } 1 2 3 4 5 6 7 8 9 10 11 12 $exception instanceof ExceptionInterface => new Response($exception->getMessage(), $this->mapExc public function __invoke(ExceptionEvent $event): void 1 { 2 $exception = $event->getThrowable(); 3 $response = match (true) { 4 $exception instanceof HttpExceptionInterface => 5 new Response($exception->getMessage(), $exception->g 6 7 8 default => new Response('Internal Server Error', Respo 9 }; 10 $event->setResponse($response); 11 } 12 

private function mapExceptionToStatusCode(ExceptionInterfa { return match (true) { $exception instanceof ArticleNotFoundException, $exception instanceof ImageNotFoundException => Respon $exception instanceof ArticleExpiredException => Respo // ... default => Response::HTTP_INTERNAL_SERVER_ERROR, }; } 1 2 3 4 5 6 7 8 9 10 

final class ShowArticleController { #[Route("/articles/{articleId}", name="blog_article_show" public function __invoke(int $articleId, ArticleRepositor { $article = $articleRepository->find($articleId); return $this->render('articles/show-article.html.twig', } } 1 2 3 4 5 6 7 8 9 

Request ID in Exception Kontext namespace App\Logger; use Monolog\Attribute\AsMonologProcessor; #[AsMonologProcessor] final class UidProcessor extends \Monolog\Processor\UidProc { } 1 2 3 4 5 6 7 8 

Recap 

Mess up your code, and you need good error handling but mess up your error handling, you’re screwed! 

Danke! 

Fin.