Performance comparision: isset vs. array_key_exists

isset_vs_array_key_exists.php

<?php

function testPerformance($name, Closure $closure, $runs)
{
    $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));

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

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

testPerformance('isset', $isset,                       10000000);
testPerformance('array_key_exists', $array_key_exists, 10000000);

results.md

$ php -n --version
PHP 7.3.15-3 (cli) (built: Feb 23 2020 07:15:44) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.3.15, Copyright (c) 1998-2018 Zend Technologies

$ php -n /tmp/bench.php 
Function call isset took 0.59805 seconds
Function call array_key_exists took 0.71361 seconds