This document discusses functional programming concepts in PHP 7 including lambda functions, closures, higher-order functions, currying, partial application, point-free style, and immutability. Examples are provided to demonstrate how these concepts can be applied to writing validation logic in a functional way using functions like pipe(), ifElse(), anyPass(), and has(). The talk encourages adopting a functional programming style for PHP code to write more reusable and composable functions.

1. Functional Programming
with PHP 7

2. About me
http://sergiors.com
Don’t worry be happy and follow me ✌

3. What we will learn?

4. Functional Programming concepts,
jargons and a lot of beautiful examples
that will be blow your mind.

5. And where I can use it?
Can I apply it on a daily
basis?

6. In your data, business logic, etc…
Of course!

7. https://speakerdeck.com/
marcelgsantos/programacao-funcional-
em-php-saia-da-zona-de-conforto
For a deeper knowledge

8. Let’s go to the party!

9. Lambda or
Anonymous function

10. $foo = function () {
};

11. Closure

12. $bar = function () use ($fuzz) {
}
It has access to external scope

13. Higher-order functions

14. Takes one or more functions as arguments
and returns a function as its result.

15. Currying

16. Currying is converting a single function of n
arguments into n functions with a single
argument each.
f(x, y, z) -> f(x)(y)(z)

17. function has($x)
{
return function (array $xss) use ($x) {
return isset($xss[$x]);
};
}
$hasName = has('name');
$hasName(['name' => 'Sérgio']); //=> true
$hasName(['yearsOld' => 26]); //=> false
has('lastName')(['lastName' => 'Siqueira']); //=> true

18. Currying vs Partial
Application

19. Partial Application,
what?

20. function has(...$args)
{
return partial(function (array $xss, $x) {
return isset($xss[$x]);
})(...$args);
}
$hasName = has('name');
$hasName(['name' => 'Sérgio']); //=> true
$hasName(['yearsOld' => 26]); //=> false
has('lastName')(['lastName' => 'Siqueira']); //=> true

21. function has(...$args)
{
return partial(function (array $xss, $x) {
return isset($xss[$x]);
})(...$args);
}
$hasName = has('name');
$hasName(['name' => 'Sérgio']); //=> true
$hasName(['yearsOld' => 26]); //=> false
has('lastName')(['lastName' => 'Siqueira']); //=> true

22. Tacit programming or
point-free style

23. function has(...$args)
{
return partial(function (array $xss, $x) {
return isset($xss[$x]);
})(...$args);
}
$hasName = has('name');
$hasName(['name' => 'Sérgio']); //=> true
$hasName(['yearsOld' => 26]); //=> false
has('lastName')(['lastName' => 'Siqueira']); //=> true

24. function partial(callable $fn, ...$args)
{
$arity = (new ReflectionFunction($fn))
->getNumberOfRequiredParameters();
return isset($args[$arity - 1])
? $fn(...$args)
: function (...$restArgs) use ($fn, $args) {
return partial($fn, ...array_merge($args, $restArgs));
};
}

25. function partial(callable $fn, ...$args)
{
$arity = (new ReflectionFunction($fn))
->getNumberOfRequiredParameters();
return isset($args[$arity - 1])
? $fn(...$args)
: function (...$restArgs) use ($fn, $args) {
return partial($fn, ...array_merge($args, $restArgs));
};
}

26. Arity: Number of arguments
a function or operator takes.

27. function partial(callable $fn, ...$args)
{
$arity = (new ReflectionFunction($fn))
->getNumberOfRequiredParameters();
return isset($args[$arity - 1])
? $fn(...$args)
: function (...$restArgs) use ($fn, $args) {
return partial($fn, ...array_merge($args, $restArgs));
};
}

28. function partial(callable $fn, ...$args)
{
$arity = (new ReflectionFunction($fn))
->getNumberOfRequiredParameters();
return isset($args[$arity - 1])
? $fn(...$args)
: function (...$restArgs) use ($fn, $args) {
return partial($fn, ...array_merge($args, $restArgs));
};
}

29. Stop!
Where I use it?

30. Okey! Let’s go to my
prelude!

31. Remember, in PHP,
array also is hashmap

32. public function validate($value, Constraint $constraint)
{
if (empty($value)) {
return $value;
}
$violation = function () use ($value, $constraint) {
$this->context->buildViolation($constraint-
>message)
->setParameter('{{ value }}', $value)
->addViolation();
};
return pipe(
function ($name) {
return preg_replace('/(d|[^sw])/u', '',
$name);
},
function ($name) {
return preg_replace('/[ntr]/', ' ',
$name);

33. function tail(array $xss)
{
return array_slice($xss, 1);
}

34. function ifElse(callable $pred)
{
return function (callable $succfn) use ($pred) {
return function (callable $failfn) use ($pred, $succfn) {
return function ($x = null) use ($pred, $succfn, $failfn) {
return $pred($x)
? $succfn($x)
: $failfn($x);
};
};
};
}

35. function id($id)
{
return $id;
}

36. function lt($x)
{
return function ($y) use ($x) {
return $x < $y;
};
}

37. function pipe(callable ...$callbacks)
{
return function ($payload) use ($callbacks) {
$rest = tail(func_get_args());
return array_reduce($callbacks, function ($payload,
$callback) use ($rest) {
return $callback(...array_merge([$payload], $rest));
}, $payload);
};
}

38. public function validate($value, Constraint $constraint)
{
if (empty($value)) {
return $value;
}
$violation = function () use ($value, $constraint) {
$this->context->buildViolation($constraint->message)
->setParameter('{{ value }}', $value)
->addViolation();
};
return pipe(
function ($name) {
return preg_replace('/(d|[^sw])/u', '', $name);
},
function ($name) {
return preg_replace('/[ntr]/', ' ', $name);
},
function ($name) {
return preg_replace('/s(?=s)/', ' ', $name);
},
function ($name) {
return preg_match_all('/w{2,}/u', trim($name));
},
ifElse(lt(1))(id)($violation)
)($value);
}

39. Immutability

40. $validate = anyPass([
[Validator::phone(), 'validate'],
[Validator::cpf(), 'validate'],
]);
$sanitize = ifElse($validate)
(function ($subject) {
return preg_replace('/D+/', '', $subject);
})
(id);
$user = $this->createQueryBuilder('u')
->where('u.email = :username')
->orWhere("JSONB_HGG(u.data, '{phones, mobile}') = :username")
->orWhere("JSONB_MGG(u.data, 'cpf') = :username")
->setParameter('username', $sanitize($username))
->getQuery()
->getOneOrNullResult();
$throw = function () {
throw new UserNotFoundException();
};
return $user === null
? $throw()
: $user;

41. function anyPass(array $preds)
{
return function ($x) use ($preds) {
return array_reduce($preds,
function (bool $prev, callable $pred) use ($x) {
return true === $prev
? $prev
: $pred($x);
}, false
);
};
}

42. $foo = anyPass([
function (array $x) {
return isset($x['mobile']);
},
function (array $x) {
return isset($x['last_name']);
}
]);
$foo(['last_name' => 'Siqueira']); //=> true
$foo(['lastName'] => 'Siqueira'); //=> false
Lack the last argument,
point-free style

43. $foo = anyPass([
has('mobile'),
has(‘last_name')
]);
$foo(['last_name' => 'Siqueira']); //=> true
$foo(['lastName'] => 'Siqueira'); //=> false

44. public function getOwner(): UserInterface
{
$data = pipe(filter(has('owner')), head, get)
($this->data['admins'] ?? []);
return new User(
$data('id'),
$data('name'),
new Email($data('email'))
);
}

45. http://github.com/sergiors/prelude

46. Thank you! 🍻
Twitter @serg1ors
Github @sergiors
http://sergiors.com