public function increment($key, $offset = 1, $initial_value = 0, $expiry = 0)
    {
        if (($prevVal = $this->get($key))) {
            if (!is_numeric($prevVal)) {
                return false;
            }

            $newVal = $prevVal + $offset;
        } else {
            $newVal = $initial_value;
        }

        $this->set($key, $newVal, $expiry);

        return $newVal;
    }