this function will let you display different content if a user is on a public or private ip address.

function ip_is_private ($ip) {
$pri_addrs = array (
'10.0.0.0|10.255.255.255', // single class A network
'172.16.0.0|172.31.255.255', // 16 contiguous class B network
'192.168.0.0|192.168.255.255', // 256 contiguous class C network
'169.254.0.0|169.254.255.255', // Link-local address also refered to as Automatic Private IP Addressing
'127.0.0.0|127.255.255.255' // localhost
);
$long_ip = ip2long ($ip);
if ($long_ip != -1) {
 foreach ($pri_addrs AS $pri_addr) {
 list ($start, $end) = explode('|', $pri_addr);
 // IF IS PRIVATE
 if ($long_ip >= ip2long ($start) && $long_ip <= ip2long ($end)) {
 return true;
 }
 }
}
 return false;
}
if ( ip_is_private ( $_SERVER['REMOTE_ADDR'] ) ) {
 echo ( "<p>".$_SERVER['REMOTE_ADDR']." is from a private address range</p>");
}
else {
 echo ($_SERVER['REMOTE_ADDR']. "%s is NOT from a private address range <br>");
}