jotting down functions

stuff.php

<?php

// Return greatest common divider of two numbers
function gcd($a, $b) {
    return $b ? gcd($b, $a % $b) : $a;
}

// Returns the least common multiple of two or more numbers.
function lcm(...$numbers): int
{
    $ans = $numbers[0];
    for ($i = 1, $max = count($numbers); $i < $max; $i++) {
        $ans = (($numbers[$i] * $ans) / gcd($numbers[$i], $ans));
    }

    return $ans;
}

lcm(12, 7); // 84
lcm(1, 3, 4, 5); // 60

/**
 * @param string $needle Such as, `/^AWS_/`
 * @param array $input An associative array
 * @return array
 */
function preg_grep_keys(string $needle, array $haystack): array {
    return array_intersect_key($haystack, array_flip(preg_grep($needle, array_keys($haystack))));
}