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Why choose Hack/HHVM over PHP7

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Presented on Feb 24, 2016.
PHP7 is out, but it is still worth to choose Hack/HHVM.

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Why choose Hack/HHVM over PHP7

  1. 1. Why choose Hack/HHVM over PHP7 Intelligence, Ltd. Yuji Otani 1 Presented on Feb 24, 2016
  2. 2. 2 • Born in Shimonoseki, Yamaguchi Prefecture • Software Engineer at Intelligence, Ltd • I love cars and programming • Be my friend on Facebook! https://www.facebook.com/yuji.otani.16 About me:
  3. 3. 3 5years → → My main experiences with programming languages: 7years 1year
  4. 4. 4 Question 1 Have you used Hack/HHVM?
  5. 5. 5 Question 2 PHP7 has been released. Are you uncertain about what to use next?
  6. 6. 6 Goal of this presentation: Convey the qualities of Hack/HHVM and make you consider it
  7. 7. 7 We have adopted Hack/HHVM in many projects here at Intelligence since 2015. The Framework of our choice is FuelPHP.
  8. 8. 8 Example: MIIDAS (job hunting service) https://miidas.jp
  9. 9. 9 Example: MyRefer (employee referral service) https://i-myrefer.jp/
  10. 10. 10 • a programming language developed by Facebook • compatible with PHP • runs on HHVM (virtual machine) • based on PHP5.6 What is Hack?
  11. 11. • bug-free and fast coding • enjoyable coding experience • fast runtime • fit for large scale systems The goals of Hack: http://growthhackjapan.com/2014-03-23-facebook-hack-released-to-the-public/
  12. 12. 12 • we wanted to challenge something new while leveraging the experience with PHP • we wanted to deliver a performant service • we wanted to keep the ease of readability and maintainability even when the system grew bigger • PHP7 was not available yet Why we chose Hack:
  13. 13. 13 At the end of last year, the big happening
  14. 14. 14 Dec 3, 2015 PHP7 was released!
  15. 15. 15 Huge performance improvements!! http://talks.php.net/fluent15#/wpbench
  16. 16. 16 • Null coalesce operator • EngineException (catchable fatal errors) • anonymous classes • scalar type hinting • return type declaration New language specifications
  17. 17. 17 • optimized for 64-bit CPUs • efficient use of CPU cache • in-memory arrays became sequences (in PHP5 they were all associative arrays) • the memory usage by arrays has improved dramatically. * PHP5 (72bytes) → PHP7 (32bytes) New data structure
  18. 18. 18 PHP7 incorporated many features from Hack/HHVM • scalar type hinting • return value declaration • great performance • lower consumption of memory for arrays • AST (abstract syntax tree) compiling
  19. 19. 19 Currently PHP faces a big turning point. That's precisely the reason why I want you to know the qualities of Hack/HHVM.
  20. 20. 20 Point 1 Powerful type hinting
  21. 21. 21 What is type hinting? You can specify the type of arguments and return values of functions. Class Sample { public static function sampleFunc(int $a): string{ return "OK"; } } //OK Sample::sampleFunc (1); //Fatal Error Sample::sampleFunc ("a");
  22. 22. 22 Type hinting in PHP Types that could be used in type hinting were gradually added. PHP5.0 :Class PHP5.1 :array PHP5.4 :Closure and function PHP7 :Scalar Type (int, float, string, bool)
  23. 23. 23 There are major differences in type hinting between Hack and PHP7
  24. 24. 24 PHP7 type hinting There are 2 modes: • Weakly typed = automatic type casting • Strongly typed = strict type checking <?php Class Sample { public static function sampleFunc(int $a): string{ return "OK"; } } // OK in both modes Sample::sampleFunc(1); // OK only in weakly typed mode Sample::sampleFunc("1");
  25. 25. 25 PHP7 type hinting • The default mode is “weakly typed” • To switch to “strongly typed” mode, it is necessary to declare it in the beginning of the source files • It’s only possible to declare “strongly typed” mode per file, i.e. it’s not possible to declare “strongly typed” mode in configuration files <?php // "Strongly typed" mode is enabled in this file only declare(strict_types=1);
  26. 26. 26 PHP7 type hinting • It is not possible to declare nullable or mixed types. • Passing Null to a function with type-hinted parameters will trigger error. <?php Class Sample { public static function sampleFunc(int $a): string{ return "OK"; } } //Fatal Error Sample::sampleFunc(null);
  27. 27. 27 Hack type hinting • Only “strongly typed” mode • Permits any type (including null) by using the “mixed” keyword <?hh Class Sample { public static function sampleFunc(mixed $a): string{ return "OK"; } } //OK Sample::sampleFunc(null); Sample::sampleFunc(1); Sample::sampleFunc(”a");
  28. 28. 28 Hack Type Hinting • Accepts Null by adding a “?” before the type hint <?hh Class Sample { public static function sampleFunc(?int $a): string{ return "OK"; } } //OK Sample::sampleFunc(null); Sample::sampleFunc(1);
  29. 29. 29 Hack Type Hinting The types of keys and values of arrays can be specified. However, it is only for static analysis, not runtime. <?hh Class Sample { public static function sampleFunc(array<int, string> $a): string{ return "OK"; } } //OK Sample::sampleFunc(array(1 => "a", 2 => "b")); Sample::sampleFunc(array(1 => 1, 2 => null));
  30. 30. 30 Hack Type Hinting It is possible to specify types in Enum. <?hh enum Size: int { MEDIUM = 1; LARGE = 2; } Class Sample { public static function sampleFunc(Size $size): string{ return "OK"; } } //OK Sample::sampleFunc(Size::LARGE); Sample::sampleFunc(2); Sample::sampleFunc(4); // This works too: it checks the type, not the value. //Error Sample::sampleFunc(”a");
  31. 31. 31 Type Hinting • “Strongly typed” only • Nullable and mixed types The specifications put emphasis on type-sensitive, large scale systems. • “Weakly typed” by default • No nullable nor mixed types The specifications put emphasis on the speed of type-agnostic development.
  32. 32. 32 Point 2 Collections
  33. 33. 33 PHP5 arrays: • Arrays and associative arrays can be used in the same way • Arrays accept values of any type • Keys can be integer or string • Values are retrieved in order of insertion, regardless of keys <?php // the code below prints “ab” $arr = array(1 => ”a", 0 => ”b"); foreach($arr as $value ) { print($value); }
  34. 34. 34 Hack Collections: • Has original collections: Vector, Map, Set and Pair • It is possible to specify the types of keys and values, though they’re not checked during runtime <?hh $a = new Map<string, string>; //OK $a->set("key1", "value1"); //OK $a->set("key2", 2); //OK $a->set(3, array());
  35. 35. 35 Hack Collection It’s not necessary to check if the key exists prior to fetching a value, and it won’t trigger a “Notice” error when the key doesn’t exist. <?hh $a = new Map<string, string>; $a->set("key1", "value1"); // $val1 becomes “value1” $val1 = $a->get("key1"); // $val2 becomes null, no “Notice” error fired $val2 = $a->get("key2");
  36. 36. 36 Map Stores key-value pairs B A D EC
  37. 37. 37 Vector Pure stack-like ordered array 21 4 53
  38. 38. 38 Set Ordered collection of unique values BA D EC
  39. 39. 39 Pair Immutable collection of exactly 2 values
  40. 40. 40 Collection • Four original collections • It is possible to specify the types of values (keys as well for Maps) The specifications put emphasis on type-sensitive, large scale systems. • Only arrays that accept any type • No concern over the types of arrays and their values The specifications put emphasis on the speed of “anything-goes” associative arrays.
  41. 41. 41 Point 3 Original specifications
  42. 42. 42 Original features: • Lambdas • Generics • Enum • Tuples • Shapes
  43. 43. 43 Enum (Enumeration of value) <?hh enum Size: int { SMALL = 0; MEDIUM = 1; LARGE = 2; X_LARGE = 3; } Enumerate values with a specific type
  44. 44. 44 Tuples <?hh list($a, $b) = testFunc(); public function testFunc() : (string, int) { return tuple(“OK”, 1); } Return multiple values ​​from a function
  45. 45. 45 Original language specification Hack/HHVM has added many original language specifications. By using Hack in your service, you can achieve: • quick development with fewer bugs • developers actually enjoy coding
  46. 46. 46 Point 4 Parallel execution
  47. 47. 47 Parallel execution It is possible to run statements in parallel by using original functions such as “Async” and “Await.” Parallel execution is possible out-of-the-box, reaching even higher performance speeds.
  48. 48. 48 Parallel execution
  49. 49. 49 Point 5 Static analysis tool
  50. 50. 50 Static analysis tool The static analysis of the code is done by hh_client. It checks for syntax errors and inconsistencies, allowing developers to fix them before runtime. Code with fewer bugs like this is only possible due to the strict type restrictions in Hack.
  51. 51. 51 You can check the program before execution. • Check for compilation errors • Type-check the arguments and return values • Check for discouraged syntax • Check for inappropriate type casting Static analysis tool * configure automatic static analysis with hhvm.hack.lang.auto_typecheck in config files.
  52. 52. 52 Point 6 Gradually adopting features from PHP7
  53. 53. 53 Continued support for both PHP5 and 7 • HHVM3.11 implements the new features in PHP7 • The direction is to support both PHP5 and PHP7 • Also possible to break backward compatibility by setting “hhvm.php7.all = 1” in the settings • Features from PHP7 can be individually enabled https://docs.hhvm.com/hhvm/configuration/INI-settings#php-7-settings
  54. 54. 54 Point 7 Great adoption record
  55. 55. 55 Great adoption record The adoption continues to grow, especially among large scale services. Wikipedia and Baidu have many commits into the source code to Hack/HHVM. https://github.com/facebook/hhvm/wiki/Users
  56. 56. 56 Although Hack/HHVM is very nice, there are also unfavorable qualities
  57. 57. 57 Release cycle Hack (HHVM) • Released every 8 weeks • Every 3rd version is turned into the LTS version, which is supported for one year PHP • Released every 1 year • Life cycle of 3 years (bug fixes 2 years, security 1 year)
  58. 58. LTS are supported for about 1 year Hack/HHVM support
  59. 59. 59 • HHVM crash: needed to monitor to restart automatically • pecl not supported: tried replacing some with golang, but currently venturing into HNI • Had to upgrade CentOS6 to CentOS7 due to sudden end of support • Most of IDEs don’t support it Some issues we faced in production
  60. 60. 60 Hard to find resources Problem
  61. 61. 61 PHP7 support in HHVM
  62. 62. 62 PHP7 support in HHVM http://hhvm.com/blog/10859/php-7-support
  63. 63. 63 TLDR; • The release of PHP7 is also fortunate to HHVM • New features in PHP7 will be available from HHVM3.11 • HHVM will continue supporting both PHP5 and PHP7 • Possible to break backward compatibility by setting “hhvm.php7.all = 1” in the settings https://docs.hhvm.com/hhvm/configuration/INI-settings#php-7-settings
  64. 64. 64 Issues related to PHP7 can be tracked on GitHub https://github.com/facebook/hhvm/labels/php7%20incompatibility
  65. 65. 65 Wrap-up • PHP7 and Hack are similar, but with different features • Hack seems to more suited to large scale systems • Hack didn’t split from PHP, it synchronizes and evolves together
  66. 66. 66 PHP specifications are community-driven, while Hack is mainly developed by Facebook. I think PHP values the “loose PHP-ness,” while Hack values the “correct practical use.” Final thoughts
  67. 67. 67 It is great to have options in the future of an excellent language like PHP!
  68. 68. 68 PHP7 is out, but it is still worth to choose Hack/HHVM!
  69. 69. 69 thank you
  70. 70. 70 This document was created with accuracy in mind, but the author does not guarantee its veracity nor its usefulness. In addition, this material was created solely by the author, and it does not represent the views, values, etc. of any organization. Disclaimer

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