Are you using IPv6?
Sadly, no. 18.191.14.104 is not an IPv6 address.
For your information, here is the code I'm using for this:
<![CDATA[
$ip = getenv("REMOTE_ADDR");
if(filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6) === false)
{
echo "
Sadly, no. $ip is not an IPv6 address.
<br>
<br>
<img src=\"NonAnimatedFlowers.gif\" alt=\"Sorry, Charlie.\">
";
}
else
{
echo "
Why, yes. $ip is indeed an IPv6 address. Well done!
<br>
<br>
<img src=\"AnimatedFlowers.gif\" alt=\"Yay!\">
";
}
]]>