Miscellany

    function cidr_to_ip($cidr_address) {
        $first = substr($cidr_address, 0, strpos($cidr_address, "/"));
        $netmask = substr(strstr($cidr_address, "/"), 1);
        $first_bin = str_pad(decbin(ip2long($first)), 32, "0", STR_PAD_LEFT);
        $netmask_bin = str_pad(str_repeat("1", (integer)$netmask), 32, "0", STR_PAD_RIGHT);
        for ($i = 0; $i < 32; $i++) {
            if ($netmask_bin[$i] == "1") {
                $last_bin .= $first_bin[$i];
                $firstfixed_bin .= $first_bin[$i];
            } else {
                $last_bin .= "1";
                $firstfixed_bin .= "0";
            }
        }
        $firstfixed = long2ip(bindec($firstfixed_bin));
        $last = long2ip(bindec($last_bin));
        return (array($firstfixed,$last));
    }