IP.php

<?php
function getIpAddress() {
return (empty(
$_SERVER['HTTP_CLIENT_IP'])?(empty($_SERVER['HTTP_X_FORWARDED_FOR'])?
$_SERVER['REMOTE_ADDR']:$_SERVER['HTTP_X_FORWARDED_FOR']):$_SERVER['HTTP_CLIENT_IP']);
}

echo 
'getIpAddress()';
?>

Or, as a one liner (broken into 2 for viewing purposes)

<?php echo (empty($_SERVER['HTTP_CLIENT_IP'])?(empty($_SERVER['HTTP_X_FORWARDED_FOR'])?
$_SERVER['REMOTE_ADDR']:$_SERVER['HTTP_X_FORWARDED_FOR']):$_SERVER['HTTP_CLIENT_IP']); ?>