PHP Spread Syntax in Array Declaration

Question

PHP supports the spread syntax for variadic functions.

In JavaScript, you can use the spread syntax to do this:

var a = [1, 2];
var b = [...a, 3, 4];         


        

Answer 1

Update: Spread Operator in Array Expression

Source: https://wiki.php.net/rfc/spread_operator_for_array

Version: 0.2
Date: 2018-10-13
Author: CHU Zhaowei, jhdxr@php.net
Status: Implemented (in PHP 7.4)

An array pair prefixed by … will be expanded in places during array definition. Only arrays and objects who implement Traversable can be expanded.

For example:

$parts = ['apple', 'pear'];
$fruits = ['banana', 'orange', ...$parts, 'watermelon'];
// ['banana', 'orange', 'apple', 'pear', 'watermelon'];

It's possible to do the expansion multiple times, and unlike argument unpacking, … can be used anywhere. It's possible to add normal elements before or after the spread operator.

Spread operator works for both array syntax(array()) and short syntax([]).

It's also possible to unpack array returned by a function immediately.

$arr1 = [1, 2, 3];
$arr2 = [...$arr1]; //[1, 2, 3]
$arr3 = [0, ...$arr1]; //[0, 1, 2, 3]
$arr4 = array(...$arr1, ...$arr2, 111); //[1, 2, 3, 1, 2, 3, 111]
$arr5 = [...$arr1, ...$arr1]; //[1, 2, 3, 1, 2, 3]

function getArr() {
  return ['a', 'b'];
}
$arr6 = [...getArr(), 'c']; //['a', 'b', 'c']

$arr7 = [...new ArrayIterator(['a', 'b', 'c'])]; //['a', 'b', 'c']

function arrGen() {
    for($i = 11; $i < 15; $i++) {
        yield $i;
    }
}
$arr8 = [...arrGen()]; //[11, 12, 13, 14]

<---------------End of Update-------------------->

First of all you are referencing the Variadic function with arrays in wrong sense.

You can create your own method for doing this, or you can better use array_merge as suggested by @Mark Baker in comment under your question.

If you still want to use spread operator / ..., you can implement something like this yourself.

<?php
function merge($a, ...$b) {
    return array_merge($a,$b);
}

$a = [1, 2];
$b = [3,4];
print_r( merge($a, ...$b));
?>

But to me, doing it like this is stupidity. Because you still have to use something like array_merge. Even if a language implements this, behind the scene the language is using merge function which contains code for copying all the elements of two arrays into a single array. I wrote this answer just because you asked way of doing this, and elegancy was your demand.

More reasonable example:

<?php
$a = [1,2,3,56,564];
$result = merge($a, 332, 232, 5434, 65);
var_dump($result);
?>

Answer 2

The spread operator in the arrays RFC has been implemented in PHP 7.4:

$ary = [3, 4, 5];
return [1, 2, ...$ary]; // same as [1, 2, 3, 4, 5]

Caveat: The unpacked array/Traversable can only have integer keys. For string keys array_merge() is still required.

Answer 3

In PHP 7.4 you can now use Spread Operators in array expressions.

$parts = ['apple', 'pear'];
$fruits = ['banana', 'orange', ...$parts, 'watermelon'];
// ['banana', 'orange', 'apple', 'pear', 'watermelon'];

Answer 4

Below PHP 7.4

$mainArray = ['element1', 'element2'];
$finalArray = array_merge($mainArray, ['element3']);
print_r($finalArray);
// Final array would be ['element1', 'element2', 'element3'];

In or Above PHP 7.4

$mainArray = ['element1', 'element2'];
$finalArray = [...$mainArray, 'element3'];
print_r($finalArray);
// Final array would be ['element1', 'element2', 'element3'];