custom pages for bots detected from DBs

[ajetrumpet]

if I have a list of 5,000 bots and their server header into in my DBs, can someone point me to a web resource that can give me any insight into how to show a custom page if a bot is detected at the render request? I can look up PHP functions myself and possibly use header(), but didn’t know if anything special was involved that I don’t already know about. so, say for instance, as a joke I want to do this:

<?php
$ip = gethostbyaddr($_SERVER['REMOTE_ADDR']);
   if (substr($ip, 0, 3) = '10.') {
      echo 'sorry, but we do not display content to USA government's automated server sniffing bots.';
}
?>

how much of a pain in the rear would it be to display custom pages for ‘‘x’’ number of automated hits? I realize that this is pointless because most are just from researching orgs the world over, but it IS a relevant question to ask. thanks.