php, arrays & functional programming
TRANSCRIPT
PHP, Arrays & Functional Programming
4/2016
Model Driven Software DevelopmentSclable transforms your knowledge into
enterprise-grade, ready-to-go Business Applications.
Sclable Business Solutions GmbHhttps://sclable.com/
4/2016
By the way:
We’re always looking forFull Stack Developers
4/2016
Sclable Platform Senior Developer
PL/PGSQL - PHP - JS← full stack →
Aviation Enthusiast
Michael Rutz
4/2016
f(x) === f(x)Immutable
y = x; f(x); x === y;No side effects
Functional Programming
4/2016
$first = 0;$second = 1;for ($i = 0; $i < 10; $i++) { echo $first . PHP_EOL; $tmp = $first; $first = $second; $second += $tmp;}
Functional Programming
Global state has changed
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function fibonacci($n, $first = 0, $second = 1) { if ($n === 0) return ''; return $first . PHP_EOL . fibonacci(--$n, $second, $first + $second);}
echo fibonacci(10);
Functional Programming
Global state untouched
Immutable
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FPHP?
Functional Programming in PHP
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Imperative design, but
Closures ✓
Functional Programming in PHP
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$ids = array_map(function ($item) { return $item->id;}, $list);
// js / ES2015let ids = list.map(item => item.id);
Functional Programming in PHP
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Implemented the right way,code readability can be improved.
Functional Programming in PHP
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https://secure.php.net/manual/en/book.array.php
Array Functions
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Performance !Nice shorthands !
Array Functions
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$idsToLoad = array_diff($idsRequired, $idsLoaded);
// e.g. cities -> countries$referencedCountryIds = array_unique([1,1,2,3]);
Array Functions
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array array_map(callable, array, array...)
bool array_walk(&array, callable)
array array_unique(array, sort_flags)
Inconsistent API
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https://github.com/sclable/array-functions
composer require sclable/array-functions
class ArrayWrap
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Normalized ParamsOO & FP Approach
class ArrayWrap
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// e.g. cities -> countries$referencedCountryIds = ArrayWrap::create($cities) ->map(function ($city) { return->countryId; }) ->unique();
e.g.
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More e.g.
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$array = array_pad([], 10, 0);foreach ($array as &$item) { $item = rand();}
// find max$max = null;foreach ($array as $item) { $max = $max === null ? $item : max($max, $item);}
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ArrayWrap::create([]) ->pad(10, 0) ->map(function () { return rand(); }) ->max();
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// [x] immutable// [x] no side effects
$emptyArr = ArrayWrap::create([]);$padded = $emptyArr->pad(10, 0);$randList = $padded->map( … );$max = $randList->max();
var_dump($emptyArr === $padded); // falsevar_dump($padded === $randList); // false
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foreach vs. array_map/array_walk
Performance Considerations
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! major performance impact on closures !
xDebug
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$ids = []foreach ($models as $model) { $ids[] = $model->id;}
$ids = array_map( function ($model) { return $model->id; }, $models);
Extract a list of ids
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Foreach vs. Array_map 1:0
Extract a list of ids
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$assigned = [];foreach ($instances as $instance) { $assigned[$instance->id] = $instance;}
$assigned = array_combine(array_map( function ($instance) {return $instance->id;}, $instances), $instances);
Assign by id
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Foreach vs. Array_map 2:0
Assign by id
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$yelled = [‘OH’, ‘SO’, ‘LOUD’];
$pssst = [];foreach ($yelled as $v) { $pssst[] = strtolower($v);}
$pssst = array_map(‘strtolower’, $yelled);
Apply native functions
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Foreach vs. Array_map 2:1
Apply native functions
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Performance.
But readability!
Conclusions
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Performance.
But readability!
Conclusions
+ It looks cool!
4/2016
Thank you.
That’s all folks!