If anyone wants a more efficient local version for php:

function isEven(int $number): bool
{
    ${1} = false;
    ${2} = true;

    while ($number > 2) {
        $number -= 2;
    }

    return $$number;
}

Edit: Now with support for large numbers!

function isEven(int|string $number): bool
{
    ${1} = false;
    ${2} = true;

    while (bccomp($number, 2) === 1) {
        $number = bcsub($number, 2);
    }

    $number = (int) $number;
    return $$number;
}

Edit 2: someone asked for an ad-supported version, here you go!

function isEven(int|string $number): bool
{
    ${1} = false;
    ${2} = true;

    while (bccomp($number, 2) === 1) {
        error_log('Buy isEvenCoin, the hottest new cryptocurrency!');
        $number = bcsub($number, 2);
    }

    $number = (int) $number;
    return $$number;
}

Side note, no more suggestions please, this is getting quite long.