foreach_vs_reduce.php

<?php
declare(strict_types=1);

$amountOfLists = 10;
$amountOfItems = 10000;

$initializeArray = function () use ($amountOfLists) {
    return array_fill(0, 10, []);
};

// With regular foreach.

$array = $initializeArray();
$start = microtime(true);

foreach (range(0, $amountOfItems) as $_) {
    $array[random_int(0, $amountOfLists - 1)][] = true;
}

printf("Regular foreach in %.4f\n", microtime(true) - $start);


// With reduce.

$array = $initializeArray();
$start = microtime(true);

$array = array_reduce(range(0, $amountOfItems), function (array $acc, $_) use ($amountOfLists) {
    $acc[random_int(0, $amountOfLists - 1)][] = true;
    return $acc;
}, $array);

printf("Regular foreach in %.4f\n", microtime(true) - $start);