Performance comparision: in-array vs. isset vs. array_key_exists

in_array_vs_isset_vs_array_key_exists.php

<?php declare(strict_types = 1);

function testPerformance($name, Closure $closure, $runs = 1000000)
{
    $start = microtime(true);
    for (; $runs > 0; $runs--)
    {
        $closure();
    }
    $end = microtime(true);

    printf("Function call %s took %.5f seconds\n", $name, $end - $start);
}

$items = [1111111];
for ($i = 0; $i < 100000; $i++) {
    $items[] = rand(0, 1000000);
}
$items = array_unique($items);
shuffle($items);

$assocItems = array_combine($items, array_fill(0, count($items), true));

$in_array = function () use ($items) {
    in_array(1111111, $items);
};

$isset = function () use ($assocItems) {
    isset($items[1111111]);
};

$array_key_exists = function () use ($assocItems) {
    array_key_exists(1111111, $assocItems);
};

testPerformance('in_array', $in_array, 100000);
testPerformance('isset', $isset, 100000);
testPerformance('array_key_exists', $array_key_exists, 100000);

result.md

$ php in_array_vs_isset_vs_array_key_exists.php 
Function call in_array took 1.51871 seconds
Function call isset took 0.14684 seconds
Function call array_key_exists took 0.22123 seconds