Benchmark custom merge vs array_replace

<?php

function customMerge(array ...$arrays) {
    $all = [];
    foreach ($arrays as $array) {
        foreach ($array as $key => $value) {
            $all[$key] = $value;
        }
    }

    return $all;
}

$first = [
    'key' => 'value',
    111 => 'chuck norris',
];

$second = [
    666 => 'hi',
    333 => 'hello world',
];

$third = [
    'key' => 'another value',
    999 => 'chuck norris',
];

foreach (['first', 'second', 'third'] as $name) {
    for ($i=0; $i < 700; $i++) {
        $ai = rand(1,999);
        ${$name}[$ai] = rand(10000,99999);
    }
}


$iterations = 50000;

$a = microtime(true);
for ($i = 0; $i < $iterations; $i++) {
    array_replace($first, $second, $third);
}
printf('array_replace (%dx): %.2fs%s', $iterations, microtime(true) - $a, PHP_EOL);

$b = microtime(true);
for ($i = 0; $i < $iterations; $i++) {
    customMerge($first, $second, $third);
}
printf('customMerge (%dx): %.2fs%s', $iterations, microtime(true) - $b, PHP_EOL);

// Final Output:
// array_replace (50000x): 1.15s
// customMerge (50000x): 17.43s