Why async and functional programming in PHP7 suck and how to get over it? www.xsolve.pl/nobodyexpects

1. Witek Adamus
PHPCon 2016, Rawa Mazowiecka

2. Why async
and
functional
programming
in PHP7 suck
and how to
get over it?

3. Who am I?

4. 5 years of
imperative
programming
2 years of
functional
programming
Back to
PHP7

5. ❏ What can
functional
programming
bring to the
table?
❏ When language
can be
described as
functional?
Table of content

6. ❏ DIY: cleaning ❏ Transparent parallelism
❏ Parallelism vs Concurrency
❏ Parallel collections
Table of content

7. Pros and cons of functional programming
Pros Cons
Efficiency Efficiency
Entry threshold Entry threshold
Mathematical
description of
reality
Mathematical
description of
reality

8. Pros and cons of functional programming
Pros Cons In result
Efficiency Efficiency Scalability
Entry threshold Entry threshold Let’s get the party
started
Mathematical
description of
reality
Mathematical
description of
reality
Shorter and more
descriptive code

9. public function someMethodWithMisleadingName(
array $mysteriousInput){
$arr = [];
foreach ($mysteriousInput as $inp) {
if ($inp > 10) { $arr[] = $inp; }
}
$arrLeft = $arrRight = $arrCenter = [];
foreach ($arr as $elem) {
$bucket = $elem <=> 20;
if ($bucket < 0) { $arrLeft[] = $elem; }
if ($bucket == 0) { $arrCenter[] = $elem; }
if ($bucket > 0) { $arrRight[] = $elem;}
}
$countLeft = count($arrLeft);
$countCenter = count($arrCenter);
$countRight = count($arrRight);
return array_sum([$countLeft, $countCenter, $countRight]) / 3;
}

10. public function someMethodWithMisleadingName(
array $mysteriousInput) {
$arr = [];
foreach ($mysteriousInput as $inp) {
if ($inp > 10) { $arr[] = $inp; }
}
$arrLeft = $arrRight = $arrCenter = [];
foreach ($arr as $elem) {
$bucket = $elem <=> 20;
if ($bucket < 0) { $arrLeft[] = $elem; }
if ($bucket == 0) { $arrCenter[] = $elem; }
if ($bucket > 0) { $arrRight[] = $elem;}
}
$countLeft = count($arrLeft);
$countCenter = count($arrCenter);
$countRight = count($arrRight);
return array_sum([$countLeft, $countCenter, $countRight]) / 3;
}
public function someMethodWithMisleadingName(
ParallelListCollection $mysteriousInput) {
return $mysteriousInput
->filter(function ($elem) { return $elem > 10; })
->partition(function ($elem) { return $elem <=> 20; })
->map(function ($bucket) { return $bucket->count(); })
->avg();
}

11. public function someMethodWithMisleadingName(
array $mysteriousInput) {
$arr = [];
foreach ($mysteriousInput as $inp) {
if ($inp > 10) { $arr[] = $inp; }
}
$arrLeft = $arrRight = $arrCenter = [];
foreach ($arr as $elem) {
$bucket = $elem <=> 20;
if ($bucket < 0) { $arrLeft[] = $elem; }
if ($bucket == 0) { $arrCenter[] = $elem; }
if ($bucket > 0) { $arrRight[] = $elem;}
}
$countLeft = count($arrLeft);
$countCenter = count($arrCenter);
$countRight = count($arrRight);
return array_sum([$countLeft, $countCenter, $countRight]) / 3;
}
public function someMethodWithMisleadingName(
ParallelListCollection $mysteriousInput) {
return $mysteriousInput
->filter(function ($elem) { return $elem > 10; })
->partition(function ($elem) { return $elem <=> 20; })
->map(function ($bucket) { return $bucket->count(); })
->avg();
}

12. Fundamental concepts in functional programming
❏ Function is a first-class citizen
❏ No side effects
❏ Immutability
❏ Lambda Calculus

13. First-class citizen
❏ Can be stored in variable and data structures
❏ Can be passed as a parameter to procedure/functions
❏ Can be returned by procedures/functions
❏ Can be instantiated inline
❏ Has it’s own identity (name independent)

14. No side effects? Immutability?
:(

15. Lambda Calculus
ƛ(x) = z

16. Lambda Calculus
ƛ(x) = z
❏ Higher-order functions
❏ Currying

17. Functional vs Object oriented programming
?

19. PHP7 is functional
…but is dirty and salty as well

20. What do I miss in PHP7 that Scala
luckily has?

21. ❏ Immutability by default
❏ Objects cloning
❏ Options
❏ Either
❏ Future
❏ Parallel collections
❏ Tail recurrency
❏ Generic types
❏ Arrow functions
❏ Pattern matching / case classes

22. Few rules to
make your
code
functional

23. Do not use
❏ reassignments
❏ if
❏ null
❏ for
❏ foreach

24. Do not use
❏ reassignments

25. $bigHouse = new Building(5);
$smallerHouse = $bigHouse->setFloors(2);
echo $bigHouse->getFloors() . PHP_EOL;
echo $smallerHouse->getFloors() . PHP_EOLl;

26. $bigHouse = new Building(5);
$smallerHouse = $bigHouse->setFloors(2);
echo $bigHouse->getFloors() . PHP_EOL; //2
echo $smallerHouse->getFloors() . PHP_EOLl; //2

27. class Building
{
protected $floors;
public function __construct(int $floors)
{
$this->setFloors($floors);
}
public function getFloors() : int
{
return $this->floors;
}
public function setFloors(int $floors) : Building
{
$this->floors = $floors;
return $this;
}
}

28. class Building
{
protected $floors;
public function __construct(int $floors)
{
$this->floors = $floors;
}
public function getFloors() : int
{
return $this->floors;
}
private function setFloors(int $floors) : Building
{
$this->floors = $floors;
return $this;
}
public function withFloors(int $floors) : Building
{
return (clone($this))->setFloors($floors);
}
}

29. $bigHouse = new Building(5);
$smallerHouse = $bigHouse->withFloors(2);
echo $bigHouse->getFloors() . PHP_EOL; //5
echo $smallerHouse->getFloors() . PHP_EOLl; //2

30. trait Copy
{
public function copy($field, $value)
{
$clone = clone $this;
$clone->$field = $value;
return $clone;
}
}

31. use PhpSlangUtilCopy;
class Building
{
use Copy;
protected $floors;
public function __construct(int $floors)
{
$this->floors = $floors;
}
public function getFloors() : int
{
return $this->floors;
}
public function withFloors(int $floors) : Building
{
return $this->copy('floors', $floors);
}
}

32. Few rules to
make your
code
functional

33. Do not use
:) reassignments
❏ if
❏ null
❏ for
❏ foreach

34. https://github.com/php-slang/php-slang

35. Do not use
:) reassignments
❏ if
❏ null
❏ for
❏ foreach
?

36. Do not use
:) reassignments
❏ if
❏ null
❏ for
❏ foreach
Option

37. Option
Monad which may contain something or nothing

38. What is a monad?
Option

39. Fishy Monad Tutorial
http://maciejpirog.github.io/fishy/ (cc-by-sa)

40. Fishy Monad Tutorial
http://maciejpirog.github.io/fishy/ (cc-by-sa)

41. Fishy Monad Tutorial
http://maciejpirog.github.io/fishy/ (cc-by-sa)

42. Fishy Monad Tutorial
http://maciejpirog.github.io/fishy/ (cc-by-sa)

43. https://github.com/php-slang/php-slang
# composer require php-slang/php-slang

44. Option
Option
NoneSome

45. Option
Option
NoneSome
map(Closure $expression)
getOrElse($default)
map(Closure $expression)
getOrElse($default)

46. Option
Option
NoneSome
map(Closure $expression)
getOrElse($default)
map(Closure $expression)
getOrElse($default)
Some($expression($this->content)
$this->content

47. Option
Option
NoneSome
map(Closure $expression)
getOrElse($default)
map(Closure $expression)
getOrElse($default)
None
$default

48. class UserRepository extends EntityRepository
{
public function findByEmail(string $email) : User
{
$user = $this->findOneByMail(['email' => $email]);
if (!$user instanceof User) {
throw new NotFoundException("oh my");
}
return $user;
}
}
public function findUserAction(string $email) :
Response
try {
$user = $this
->userRepository
->findByEmail($email);
return new Response($user);
} catch (NotFoundException $exception) {
return new Response([],
Response::HTTP_NOT_FOUND);
}
}

49. class UserRepository extends EntityRepository
{
public function findByEmail(string $email) : Option
{
return Option::of($this>findOneByMail(['email' => $email]));
}
}
public function findUserAction(string $email) : Response
return $this
->userRepository
->findByEmail($email));
->map(function (User $user) { return new Response($user); })
->getOrElse(new Response('', Response::HTTP_NOT_FOUND));
}

50. class UserRepository extends EntityRepository
{
public function findByEmail(string $email) : User
{
$user = $this->findOneByMail(['email' => $email]);
if (!$user instanceof User) {
throw new NotFoundException("oh my");
}
return $user;
}
}
public function findUserAction(string $email) : Response
try {
$user = $this
->userRepository
->findByEmail($email);
return new Response($user);
} catch (NotFoundException $exception) {
return new Response([], Response::HTTP_NOT_FOUND);
}
}
class UserRepository extends EntityRepository
{
public function findByEmail(string $email) : Option
{
return Option::of(
$this>findOneByMail(['email' => $email]));
}
}
public function findUserAction(string $email) : Response
return $this
->userRepository
->findByEmail($email));
->map(function (User $user) {
return new Response($user); })
->getOrElse(
new Response('', Response::HTTP_NOT_FOUND));
}

51. Option
How about nesting

52. public function displayNameForUser(string $email) : string
{
$this
->userRepository
->findByEmail($email)
->get()
->getFirstName();
}

53. public function displayNameForUser(string $email) : string
{
$this
->userRepository
->findByEmail($email)
->map(function (User $user) {
return $user->firstName;
})
->getOrElse('oh my');
}

54. public function displayNameForUser(string $email) : ???
{
$this
->userRepository
->findByEmail($email)
->map(function (User $user) {
return $user->getFirstName();
});
}

55. public function displayNameForUser(string $email) : ???
{
$this
->userRepository
->findByEmail($email)
->map(function (User $user) {
return $user->getFirstName();
});
}
?

56. public function displayNameForUser(string $email) : ???
{
$this
->userRepository
->findByEmail($email)
->map(function (User $user) {
return $user->getFirstName();
});
}
Option<Option<String>>

57. public function displayNameForUser(string $email) : Option
{
$this
->userRepository
->findByEmail($email)
->flatMap(function (User $user) {
return $user->getFirstName();
});
}

58. public function displayNameForUser(string $email) : string
{
$this
->userRepository
->findByEmail($email)
->flatMap(function (User $user) {
return $user->getFirstName();
})
->getOrElse($email);
}

59. public function displayNameForUser(string $email) : string
{
$this
->userRepository
->findByEmail($email)
->flatMap(function (User $user) {
return $user->getFirstName();
})
->getOrCall(function () use ($email) {
$this->getAlternative($email);
});
}

60. public function displayNameForUser(string $email) : string
{
$this
->userRepository
->findByEmail($email)
->flatMap(function (User $user) {
return $user->getFirstName();
})
->getOrCall($this->getAlternative($email));
}

61. public function displayNameForUser(string $email) : string
{
$this
->userRepository
->findByEmail($email)
->flatMap(function (User $user) {
return $user->getFirstName();
})
->getOrCall($this->getAlternative($email));
}
public function getAlternative(string $email) : Closure
{
return function () use (string $email) : string {
return $this->doSomethingElseWith($email);
};
}

62. Few rules to
make your
code
functional

63. Do not use
:) reassignments
:) if
:) null
❏ for
❏ foreach

64. Shortened notation for
anonymous functions

65. public function displayNameForUser(string $email) : string
{
return $this
->userRepository
->findByEmail($email)
->flatMap(function (User $user) {
return $user->getFirstName();
})
->getOrCall($this->getAlternative($email));
}
public function getAlternative(string $email) : Closure
{
return function () use (string $email) : string {
return $this->doSomethingElseWith($email);
};
}

66. public function displayNameForUser(string $email) : string
{
$this
->userRepository
->findByEmail($email)
->flatMap((User $user) => $user->getFirstName())
->getOrCall(() => $this->doSomethingElseWith($email))
}
:(

67. Generic types

68. public function maybeSomething(string $email) : Option
{
...
}

69. public function maybeSomething(string $email) : Option<string>
{
...
}

70. public function maybeSomething(string $email) : Option<string>
{
...
}
❏ Version: 0.4.0
❏ Date: 2016-01-06
❏ Author: Ben Scholzen 'DASPRiD' mail@dasprids.de, Rasmus Schultz rasmus@mindplay.dk
❏ Status: Draft
❏ First Published at: http://wiki.php.net/rfc/generics
:(

71. /**
* @return Option<string>
*/
public function maybeSomething(string $email) : Option
{
...
}
https://github.com/phpDocumentor/fig-standards/blob/master/proposed/phpdoc.md
:(

72. What do I miss in PHP7 that Scala
luckily has?

73. :) Immutability by default
:) Objects cloning
:) Options
❏ Either
❏ Future
❏ Parallel collections
❏ Tail recurrency
:( Generic types
:( Arrow functions
❏ Pattern matching / case classes

74. Either

75. Either
Either
RightLeft

76. Either
Either
RightLeft
left(Closure $expr): Either
right(Closure $expr): Either
get()
left(Closure $expr): Either
right(Closure $expr): Either
get()

77. public function findUserAction(string $email) : Response
try {
$user = $this
->userRepository
->findByEmail($email);
return new Response($user);
} catch (NotFoundException $exception) {
return new Response([], Response::HTTP_NOT_FOUND);
}
}

78. public function findUserAction(string $email) : Response
try {
$user = $this
->userRepository
->findByEmail($email);
return new Response($user);
} catch (NotFoundException $exception) {
return new Response([], Response::HTTP_NOT_FOUND);
} catch (ExternalServiceResponseException $exception) {
return new Response([], Response::HTTP_FAILED_DEPENDENCY);
} catch (IncorrectEmailException $exception) {
return new Response([], Response::HTTP_BAD_REQUEST);
} catch (UserNotAllowedException $exception) {
return new Response([], Response::HTTP_FORBIDDEN);
}
}
“Co jest piękniejszego niż rdest? No chyba tylko bylina rdestu, bo rzadziej występuje.”
Ohanhutep

79. interface ServiceError {}
class NotFound implements ServiceError {}
class ServiceNotWorking implements ServiceError {}
class Param2IsPoorlyFormatted implements ServiceError {}
public function getSomethingNontrivial(string $param1, string $param2, string $param3) : Either
{
...
}
Either<ServiceError, User>

80. public function exampleAction(
string $param1, string $param2, string $param3) : Response {
return $this
->userService
->getSomethingNontrivial($param1, $param2, $param3)
->left(function (ServiceError $someKindOfFailure) : Response {
new Case(ServiceNotWorking::class, new Response('', Response::HTTP_FAILED_DEPENDENCY)),
new Case(Param2IsPoorlyFormatted::class, new Response('', Response::HTTP_BAD_REQUEST)),
new Case(NotFound()::class, new Response([], Response::HTTP_NOT_FOUND));
})
->right(function (User $nonTrivialAllRight) : Response {
return new Response($nonTrivialAllRight, Response::HTTP_OK);
})
->get();
}

81. public function getSomethingNontrivial(
string $param1, string $param2, string $param3) : Either
{
return $this
->translateParam2($param2)
->map(function ($param2Translated) {
return new Right($this->getUserBy($param2Translated));
})
->getOrElse(new Left(new Param2IsPoorlyFormatted()));
}

82. public function getSomethingNontrivial(string $param1, string $param2, string $param3) : Either
{
return $this
->translateParam2($param2)
->map($this->handleWithTranslatedParam($param1, $param3))
->getOrElse(new Left(new Param2IsPoorlyFormatted()));
}
public function handleWithTranslatedParam(string $param1, string $param3) : Clojure
{
return function (Param2Translated $param2Translated) use ($param1, $param3) : Either {
return $this
->someOtherMagic($param2Translated, $param1, $param3)
->map(function (User $magicResult) use ($param1, $param3) : Either {
return new Right($magicResult);
})
->getOrElse(new Left(new ServiceNotWorking()));
};
}

83. What do I miss in PHP7 that Scala
luckily has?

84. :) Immutability by default
:) Objects cloning
:) Options
❏ Either
❏ Future
❏ Parallel collections
❏ Tail recurrency
:( Generic types
:( Arrow functions
❏ Pattern matching / case classes

85. Pattern Matching

86. public function exampleAction(string $param1, string $param2, string $param3) : Response
{
return $this
->userService
->getSomethingNontrivial($param1, $param2, $param3)
->left(function (ServiceError $someKindOfFailure) : Response {
return (Match::of($someKindOfFailure))->match(
new Case(ServiceNotWorking::class, new Response('', Response::HTTP_FAILED_DEPENDENCY)),
new Case(Param2IsPoorlyFormatted::class, new Response('', Response::HTTP_BAD_REQUEST)),
new Case(NotFound::class, new Response([], Response::HTTP_NOT_FOUND));
})
->right(function (User $nonTrivialAllRight) : Response {
return new Response($nonTrivialAllRight, Response::HTTP_OK);
})
->get();
}

87. def update(id: String): Action[JsValue] = Action.async(parse.json) { request =>
user.update(id, userConverterFactory.of(request.body).toInput)
.map {
case Right(user) => Ok(user)
case Left(UserService.UserNotFound) => NotFound
case Left(UserService.VersioningMissmatch) => NotAcceptable
case Left(UserService.NoModificationsAllowed) => Locked
case Left(UserService.InvalidPayload) => BadRequest
}
}

88. What do I miss in PHP7 that Scala
luckily has?

89. :) Immutability by default
:) Objects cloning
:) Options
:) Either
❏ Future
❏ Parallel collections
❏ Tail recurrency
:( Generic types
:( Arrow functions
:)/:( Pattern matching / case classes

90. Parallel collections

91. public function multiplyBy(
array $input, float $multiplication): array
{
$output = [];
foreach($input as $number)
{
$output[] = $number * $multiplication;
}
return $output;
}

92. use PhpSlangCollectionListCollection;
...
public function beautifulMultiplyBy(
array $input, float $multiplication) : ListCollection
{
return (new ListCollection($input))
->map(function ($number) use ($multiplication) {
return $number * $multiplication;
});
}

93. public function multiplyOddsBy(
array $input, float $multiplication): array
{
$output = [];
foreach ($input as $number) {
if ($number % 2 !== 0) {
$output[] = $number * $multiplication;
}
}
return $output;
}

94. public function beautifulMultiplyOddsBy(
array $input, float $multiplication) : ListCollection
{
return (new ListCollection($input))
->filter(function ($number) {
return $number % 2 !== 0;
})
->map(function ($number) use ($multiplication) {
return $number * $multiplication;
});
}

95. public function accumulatedText(array $words) : string
{
$text = '';
foreach ($words as $word) {
$text .= $word . ' ';
}
return $text;
}

96. public function accumulatedText(array $words) : string
{
return (new ListCollection($words))
->fold('', function (string $acumulator, string $word) {
return $acumulator . $word . ' ';
});
}

98. (new ListCollection([1,2,3,4]))->tail(); //ArrayCollection([2,3,4])

99. Few rules to
make your
code
functional

100. Do not use
:) reassignments
:) if
:) null
:) for
:) foreach

101. Parallelism vs Concurrency

104. Future

105. public function nonBlockingGet(string $id): Future
{
...
}
public function exampleAction(string $id1) : Response
{
return $this
->nonBlockingService
->nonBlockingGet($id)
->map(function (NonBlockingGetResult $output) {
return new Response($output);
})
->await();
}

106. public function nonBlockingGet(string $id): Future
{
...
}
public function exampleAction(string $id1) : Response
{
return $this
->nonBlockingService
->nonBlockingGet($id)
->map(function (NonBlockingGetResult $output) {
return new Response($output);
})
->await();
}
Future<NonBlockingGetResult>
Jak powinno to wyglądać?

107. public function nonBlockingGet(string $id): Future
{
...
}
public function exampleAction(string $id1) : Response
{
return $this
->nonBlockingService
->nonBlockingGet($id)
->map(function (NonBlockingGetResult $output) {
return new Response($output);
})
->await();
}
Future<NonBlockingGetResult>
Jak powinno to wyglądać?
Future<Response>

108. public function nonBlockingGet(string $id): Future
{
...
}
public function exampleAction(string $id1) : Response
{
return $this
->nonBlockingService
->nonBlockingGet($id)
->map(function (NonBlockingGetResult $output) {
return new Response($output);
})
->await();
}
Future<NonBlockingGetResult>
Jak powinno to wyglądać?
Future<Response>
Response

109. public function nonBlockingGet(string $id): Future
{
...
}
public function exampleAction(string $id1, string $id2, string $id3) : Response
{
return Future::all([
$this->nonBlockingService1->nonBlockingGet($id1),
$this->nonBlockingService2->nonBlockingGet($id2),
$this->nonBlockingService3->nonBlockingGet($id3),
])
->map(function ($output) {
return new Response($output);
})
->await();
}
Jak powinno to wyglądać?

110. public function nonBlockingGet(string $id): Future
{
...
}
public function exampleAction(string $id1, string $id2, string $id3) : Response
{
return Future::all([
$this->nonBlockingService1->nonBlockingGet($id1),
$this->nonBlockingService2->nonBlockingGet($id2),
$this->nonBlockingService3->nonBlockingGet($id3),
])
->map(function ($output) {
return new Response($output);
})
->await();
}
Jak powinno to wyglądać?

111. Future & Parallel collections

112. use PhpSlangCollectionListCollection;
...
public function beautifulMultiplyBy(
array $input, float $multiplication) : ListCollection
{
return (new ListCollection($input))
->map(function ($number) use ($multiplication) {
return $number * $multiplication;
});
}

113. use PhpSlangCollectionParallelListCollection;
...
public function beautifulMultiplyBy(
array $input, float $multiplication) : ParallelListCollection
{
return (new ParallelListCollection($input))
->map(function ($number) use ($multiplication) {
return $number * $multiplication;
});
}

114. class ParallelListCollection extends ListCollection
{
public function map(Closure $func)
{
return Future::all(
(new ArrayCollection($this->elements))
->map(function ($element) use ($func) {
return new Future(function () use ($func, $element) {
return $func($element);
});
})
->toArray())
->await();
}
}

115. class ParallelListCollection extends ListCollection
{
public function map(Closure $func)
{
return Future::all(
(new ArrayCollection($this->elements))
->map(function ($element) use ($func) {
return new Future(function () use ($func, $element) {
return $func($element);
});
})
->toArray())
->await();
}
}
ArrayCollection<Future<mixed>>
Future<ArrayCollection<mixed>>
ArrayCollection<mixed>

116. use PhpSlangCollectionParallelListCollection;
...
public function asyncChainedComputationExample(array $input) : ParallelListCollection
{
return (new ParallelListCollection($input))
->map($this->transformationOne())
->map($this->transformationTwo())
->map($this->transformationThree();
}

117. use PhpSlangCollectionParallelListCollection;
...
public function asyncChainedComputationExample(array $input) : ParallelListCollection
{
return (new ParallelListCollection($input))
->map($this->transformationOne())
->map($this->transformationTwo())
->map($this->transformationThree();
}

118. use PhpSlangCollectionParallelListCollection;
...
public function asyncChainedComputationExample(array $input) : ParallelListCollection
{
return (new ParallelListCollection($input))
->map(function ($number) {
return Option::of($number)
->map($this->transformationOne())
->map($this->transformationTwo())
->map($this->transformationThree()
->get();
});
}

119. use PhpSlangCollectionParallelListCollection;
…
public function asyncChainedComputationExample(array $input) : ParallelListCollection
{
return (new ParallelListCollection($input))
->map(function ($number) {
return Option::of($number)
->map($this->transformationOne())
->map($this->transformationTwo())
->map($this->transformationThree()
->get();
});
}

120. What do I miss in PHP7 that Scala
luckily has?

121. :) Immutability by default
:) Objects cloning
:) Options
:) Either
:)/:( Future
:) Parallel collections
❏ Tail recurrency
:( Generic types
:( Arrow functions
:)/:( Pattern matching / case classes

122. Tail recurrency

123. def fibonacci(index : Int) : Int = index match {
case 0 | 1 => index
case _ => fibonacci(index - 1 ) + fibonacci(index - 2)
}
function fibonacci(int $index) : int
{
return in_array($index, [0, 1])
? $index
: fibonacci($index - 1) + fibonacci($index - 2);
}

124. def fibonacci(index : Int) : Int = index match {
case 0 | 1 => index
case _ => fibonacci(index - 1 ) + fibonacci(index - 2)
}
function fibonacci(int $index) : int
{
return in_array($index, [0, 1])
? $index
: fibonacci($index - 1) + fibonacci($index - 2);
}
echo fibonacci(123123123123);
Fatal error: Maximum function nesting level of '...' reached, aborting!

125. ini_set('xdebug.max_nesting_level', 9999999);
?

126. def fibonacci(index: Int): Int = {
var a = 0
var b = 1
var i = 0
while (i < index) {
val c = a + b
a = b
b = c
i = i + 1
}
return a
}
function fibonacci(int $index) : int
{
$a = 0;
$b = 1;
$i = 0;
while ($i < $index) {
$c = $a + $b;
$a = $b;
$b = $c;
$i += 1;
}
return $a;
}

127. def recursiveFibonacci(n: Int, a:Int, b:Int): Int =
n match {
case 0 => a
case _ => recursiveFibonacci( n-1, b, a+b )
}
def fibonacci( n : Int) : Int =
recursiveFibonacci( n, 0, 1)
function recursiveFibonacci(int $n, int $a, int $b) {
return ($n == 0)
? $a
: recursiveFibonacci($n - 1, $b, $a + $b);
}
function fibonacci(int $n) : int
{
return recursiveFibonacci($n, 0, 1);
}

128. def fibonacci(index : Int) : Int = index match {
case 0 | 1 => index
case _ => fibonacci(index - 1 ) + fibonacci(index - 2)
}
function fibonacci(int $index) : int
{
return in_array($index, [0, 1])
? $index
: fibonacci($index - 1) + fibonacci($index - 2);
}

129. def recursiveFibonacci(n: Int, a:Int, b:Int): Int =
n match {
case 0 => a
case _ => recursiveFibonacci( n-1, b, a+b )
}
def fibonacci( n : Int) : Int =
recursiveFibonacci( n, 0, 1)
function recursiveFibonacci(int $n, int $a, int $b) {
return ($n == 0)
? $a
: recursiveFibonacci($n - 1, $b, $a + $b);
}
function fibonacci(int $n) : int
{
return recursiveFibonacci($n, 0, 1);
}
:(

130. Tail recurrency
Trampolines

131. Recurrency

132. Recurrency Trampoline

133. <?php
namespace PhpSlangUtilTrampoline;
...
class Trampoline
{
/**
* @var TrampolineResult
*/
var $expression;
public function __construct(Closure $expression)
{
$this->expression;
}
public function run()
{
$result = new Bounce(function () {
return ($this->expression)();
});
while ($result instanceof Bounce) {
$result = $result->run();
}
return $result->run()->get();
}
}
interface TrampolineResult
{
public function run() : TrampolineResult;
public function get();
}
class Bounce implements TrampolineResult {...}
class Done implements TrampolineResult {...}

134. function recursiveFibonacci(int $n, int $a, int $b) {
return ($n == 0)
? $a
: recursiveFibonacci($n - 1, $b, $a + $b);
}
function fibonacci($n)
{
return recursiveFibonacci($n, 0, 1);
}
echo fibonacci(8);

135. function recursiveFibonacci(int $n, int $a, int $b) {
return ($n == 0)
? new Done($a)
: new Bounce(function () use ($n, $b, $a) {
return recursiveFibonacci($n - 1, $b, $a + $b);
});
}
function fibonacci($n)
{
return (new Trampoline(function () use ($n) {
return recursiveFibonacci($n, 0, 1);
}))->run();
}
echo fibonacci(8);

136. What do I miss in PHP7 that Scala
luckily has?

137. :) Immutability by default
:) Objects cloning
:) Options
:) Either
:)/:( Future
:) Parallel collections
:) Tail recurrency
:( Generic types
:( Arrow functions
:)/:( Pattern matching / case classes

139. Conclusions
● Don’t be afraid of monads
● Don’t set traps for your team
● Learn Haskell, Clojure, Scala, F#, JavaScript -> TypeScript

140. Witek Adamus
witold.adamus@xsolve.pl

141. xsolve.pl/nobodyexpects