CODEWITHSUNDEEP
phparrayslist-comprehensionhigher-order-functionslanguage-comparisons
Darren Newton
Darren Newton

Reputation: 2877

Does PHP have an equivalent to Python's list comprehension syntax?

Python has syntactically sweet list comprehensions:

S = [x**2 for x in range(10)]
print S;
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

In PHP I would need to do some looping:

$output = array();
$Nums = range(0,9);

foreach ($Nums as $num) 
{
    $out[] = $num*=$num;
}
print_r($out);

to get:

Array ( [0] => 0 [1] => 1 [2] => 4 [3] => 9 [4] => 16 [5] => 25 [6] => 36 [7] => 49 [8] => 64 [9] => 81 )

Is there anyway to get a similar list comprehension syntax in PHP? Is there anyway to do it with any of the new features in PHP 5.3?

Thanks!

Upvotes: 90

Views: 25968

Answers (4)

Daidon
Daidon

Reputation: 756

Since PHP 7.4 you can also use arrow functions in array_map:

<?php

$nums = range(0,9);
print_r(array_map(fn($x) => $x*$x,$nums));

// Array
// (
//     [0] => 0
//     [1] => 1
//     [2] => 4
//     [3] => 9
//     [4] => 16
//     [5] => 25
//     [6] => 36
//     [7] => 49
//     [8] => 64
//     [9] => 81
// )

See live

Upvotes: 3

Athari
Athari

Reputation: 34293

In .NET, the equivalent of Python's "syntactically sweet list comprehensions" is LINQ. And in PHP, there're several ports of it, including YaLinqo library*. Syntactically, it's closer to SQL rather than a sequence of traditional constructs with for and if, but functionally, it's similar:

$a = Enumerable::range(0, 10)->select('$v * $v');

This produces an iterator which can either be output to console:

var_dump($a->toArray()); // by transforming the iterator to an array
echo $a->toString(', '); // or by imploding into a string

or iterated over using foreach:

foreach ($a as $i)
    echo $i, PHP_EOL;

Here, '$v * $v' is a shortcut for function ($v) { return $v * $v; } which this library supports. Unfortunately, PHP doesn't support short syntax for closures, but such "string lambdas" can be used to make the code shorter.

There're many more methods, starting with where (if equivalent) and ending with groupJoin which performs joining transformation with grouping.

* developed by me

Upvotes: -2

David Goodwin
David Goodwin

Reputation: 4318

PHP 5.5 may support list comprehensions - see the mailing list announcement:

And further discussion:

Upvotes: 5

Paul Dixon
Paul Dixon

Reputation: 301055

Maybe something like this?

$out=array_map(function($x) {return $x*$x;}, range(0, 9))

This will work in PHP 5.3+, in an older version you'd have to define the callback for array_map separately

function sq($x) {return $x*$x;}
$out=array_map('sq', range(0, 9));

Upvotes: 105

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