Has 5s recursive method to find numbers with 5s in them.

no-fives.php

/**
 * Does this number have 5s?
 *
 * @param $number Number to check.
 *
 * @since 1.0.0
 *
 * @return bool
 */
private function hasFive($number): bool
{
    $number = abs($number);

    while ($number) {

        if ($number % 10 == 5) {
            return true;
        }

        $number = floor($number / 10);

        return $this->hasFive($number);
    }

    return false;
}