Content based by IP

[bahawolf]

I'm looking to play a trick on my friend because he is Head of Security, I'd like this hacked page that I made in HTML to display, only to him because of his IP.
So far I have this code, and I'd like to insert it into index.php so it'd affect the main page.. any clues where to go next?

$userip = 'the IP of the person';
if ($_SERVER['REMOTE_ADDR'] == $userip OR $_SERVER['HTTML_CLIENT_IP'] == $userip)
{
// this is the person's IP address, so go ahead and do what you want
}
else
{
// this is not the person's IP, so do the normal thing
}

Thanks to daemon at vbulletin.com for giving me the above code, and he reccomended to get further help here. Thanks in advance.