Exception handling - classic and fancy

Exceptions are an integral part of PHP. PHP introduced them long ago, but handling has changed over the last versions. So the classic part contains a solid introduction to exception architecture, handling and how to use it. The fancy part will show some examples about modern exception logging.

Transcript

1. Tommy Mühle | tommy-muehle.io Exception handling classic & fancy 1
2. Tommy Mühle | tommy-muehle.io Tommy Mühle 
 Software Engineer Author 2
3. Tommy Mühle | tommy-muehle.io What is an Exception? 3
4. Tommy Mühle | tommy-muehle.io Tommy Mühle | tommy-muehle.io 4 „An exception is an event, which occurs during the execution of a program, that disrupts the normal flow of the program's instructions.“ https:/ /docs.oracle.com
5. Tommy Mühle | tommy-muehle.io 5 http://php.net/manual/en/class.exception.php
6. Tommy Mühle | tommy-muehle.io 6 http://php.net/manual/en/class.errorexception.php
7. Tommy Mühle | tommy-muehle.io Catching 7
8. Tommy Mühle | tommy-muehle.io 8 /* @var $connection \Doctrine\DBAL\Connection */ $connection->beginTransaction(); try { // ... $connection->commit(); } catch (\Exception $exception) { $connection->rollBack(); throw $exception; }
9. /* @var $connection \Doctrine\DBAL\Connection */ $connection->beginTransaction(); try { // ... $connection->commit(); } catch (Doctrine\DBAL\DBALException $exception) { $connection->rollBack(); } catch (\Exception $exception) { // ... throw $exception; } Tommy Mühle | tommy-muehle.io 9
10. Tommy Mühle | tommy-muehle.io 10 /* @var $connection \Doctrine\DBAL\Connection */ $connection->beginTransaction(); try { // ... $connection->commit(); } catch (\Exception $exception) { $connection->rollBack(); throw $exception; } finally { /* @var $logger \Monolog\Logger */ $logger->info('...'); }
11. Tommy Mühle | tommy-muehle.io If you throw something, you have to catch it. 11
12. Tommy Mühle | tommy-muehle.io Handling 12
13. Tommy Mühle | tommy-muehle.io 13 function my_handler($exception) { echo 'Got it: ' . $exception->getMessage(); } set_exception_handler('my_handler'); throw new Exception('Take this!');
14. Tommy Mühle | tommy-muehle.io PHP version specifications 14
15. Tommy Mühle | tommy-muehle.io PHP 5 15
16. Tommy Mühle | tommy-muehle.io PHP 5 16
17. Tommy Mühle | tommy-muehle.io It’s dead, Jim. 17
18. Tommy Mühle | tommy-muehle.io Exception hierarchy 18
19. Tommy Mühle | tommy-muehle.io 19 http://php.net/manual/en/spl.exceptions.php
20. Tommy Mühle | tommy-muehle.io Error as exception 20
21. Tommy Mühle | tommy-muehle.io 21 function exception_error_handler ($severity, $message, $file, $line) { throw new ErrorException ($message, 0, $severity, $file, $line); } set_error_handler('exception_error_handler'); strpos(); // Trigger exception
22. Tommy Mühle | tommy-muehle.io PHP 7 22
23. Tommy Mühle | tommy-muehle.io PHP 7 22
24. Tommy Mühle | tommy-muehle.io NEW Advanced exception hierarchy 23
25. Tommy Mühle | tommy-muehle.io 24 http://php.net/manual/en/language.errors.php7.php
26. Tommy Mühle | tommy-muehle.io 25 http://php.net/manual/en/class.throwable.php
27. Tommy Mühle | tommy-muehle.io 26 http://php.net/manual/en/class.error.php
28. Tommy Mühle | tommy-muehle.io 27 try { // ... } catch (Error $error) { // ... } catch (Exception $exception) { // ... }
29. Tommy Mühle | tommy-muehle.io PHP 7.1 28
30. Tommy Mühle | tommy-muehle.io Catching Multiple Exception Types 29
31. try { // ... } catch (LengthException | OutOfRangeException $exception) { // ... } catch (Exception $exception) { // ... } Tommy Mühle | tommy-muehle.io 30
32. Tommy Mühle | tommy-muehle.io Throw Error in Extensions 31
33. Tommy Mühle | tommy-muehle.io 32 try { $myDateTime = unserialize('O:8:"DateTime":...";}'); // ... } catch (Error $error) { // ... }
34. Tommy Mühle | tommy-muehle.io Best practices 33
35. Tommy Mühle | tommy-muehle.io Build custom exceptions upon SPL ones. 34
36. class FileNotFoundException extends InvalidArgumentException { } class FileNotReadableException extends RuntimeException { } Tommy Mühle | tommy-muehle.io 35 Build upon SPL exceptions
37. Tommy Mühle | tommy-muehle.io Differentiate between logical and runtime exceptions. 36
38. Tommy Mühle | tommy-muehle.io Help developers with creating logical exceptions. 37
39. Tommy Mühle | tommy-muehle.io Create unavoidable
 runtime exceptions 
 if necessary. 38
40. Tommy Mühle | tommy-muehle.io Create fully qualified 
 named exceptions. 39
41. Tommy Mühle | tommy-muehle.io 40 class NotFoundException extends Exception { // ... } Avoid unconcrete names
42. class FileNotReadableException extends RuntimeException { } Tommy Mühle | tommy-muehle.io 41 Use fully qualified names
43. Tommy Mühle | tommy-muehle.io Add codes for 
 your exceptions. 42
44. Tommy Mühle | tommy-muehle.io 43 class FileNotReadableException extends RuntimeException { public function __construct(string $filename) { $message = sprintf('Cannot read %s!', $filename); $code = 666; parent::__construct($message, $code, null); } } Use specific codes
45. Tommy Mühle | tommy-muehle.io Use named constructors for specific use cases. 44
46. Tommy Mühle | tommy-muehle.io 45 $url = 'unreachable.tld'; if ('' === $url) { throw new InvalidUrlException('Blank url are invalid!'); } if ('' === parse_url($url, PHP_URL_SCHEME)) { $message = sprintf('The url %s has no scheme!', $url); throw new InvalidUrlException($message); } // ... Avoid inline message generation
47. Tommy Mühle | tommy-muehle.io 46 class InvalidUrlException extends InvalidArgumentException { private static function create(string $reason) { return new static($reason); } public static function blankUrl() { return static::create('Blank url are invalid!'); } } Use named constructors
48. Tommy Mühle | tommy-muehle.io 47 class InvalidUrlException extends InvalidArgumentException { // ... public static function blankUrl() { return static::create('Blank url are invalid!'); } public static function noScheme(string $url) { $reason = sprintf('The url %s has no scheme!', $url); return static::create($reason); } // ... } One method for each case
49. Tommy Mühle | tommy-muehle.io 48 $url = 'unreachable.tld'; if ('' === $url) { throw InvalidUrlException::blankUrl(); } if ('' === parse_url($url, PHP_URL_SCHEME)) { throw InvalidUrlException::noScheme($url); } // ...
50. Tommy Mühle | tommy-muehle.io Centralize own perseverative exceptions. 49
51. Tommy Mühle | tommy-muehle.io Writing code to support PHP 5.x and 7 exceptions. 50
52. Tommy Mühle | tommy-muehle.io 51 try { // Code that may throw an Exception or Error. } catch (Throwable $exception) { // Executed only in PHP 7, // will not match in PHP 5.x } catch (Exception $exception) { // Executed only in PHP 5.x, // will not be reached in PHP 7 }
53. Tommy Mühle | tommy-muehle.io And now show 
 me some fancy stuff 52
54. Tommy Mühle | tommy-muehle.io 53
55. Tommy Mühle | tommy-muehle.io You send critical data to somebody else. 54
56. Tommy Mühle | tommy-muehle.io 55 https://rollbar.com/demo/demo/
57. Tommy Mühle | tommy-muehle.io 55 https://rollbar.com/demo/demo/ https://angel.co/bugsnag/jobs
58. Tommy Mühle | tommy-muehle.io 55 https://rollbar.com/demo/demo/ https://angel.co/bugsnag/jobs https://www.g2crowd.com/products/raygun-crash-reporting/details
59. Tommy Mühle | tommy-muehle.io 56
60. Tommy Mühle | tommy-muehle.io Tommy Mühle | tommy-muehle.io 57 „Sentry is 100% open source. All features are built in the open and can be followed and contributed to on GitHub.“ https:/ /sentry.io/about
61. Tommy Mühle | tommy-muehle.io 58 https://github.com/getsentry/sentry
62. Tommy Mühle | tommy-muehle.io 59 https://hub.docker.com/_/sentry/
63. Tommy Mühle | tommy-muehle.io Client usage 60
64. Tommy Mühle | tommy-muehle.io 61 $sentryClient = new Raven_Client( 'https://<key>:<secret>@sentry.io/<project>' ); // or $sentryClient->install(); $error_handler = new Raven_ErrorHandler($sentryClient); $error_handler->registerExceptionHandler(); $error_handler->registerErrorHandler(); $error_handler->registerShutdownFunction();
65. Tommy Mühle | tommy-muehle.io 62 $sentryClient->captureException($exception, [ 'extra' => [ 'php_version' => phpversion(), 'foo' => 'bar', // ... ], 'logger' => 'default', 'tags' => ['key' => 'value'], // group event by 'fingerprint' => ['{{ default }}', 'other value'], ]);
66. Tommy Mühle | tommy-muehle.io 63
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70. Tommy Mühle | tommy-muehle.io 67
71. Questions?
72. Thank you! Slides http:/ /bit.ly/2kzZkjx Images https:/ /pixabay.com/ @tommy_muehle