$proxy_headers = array(
    'HTTP_VIA',
    'HTTP_X_FORWARDED_FOR',
    'HTTP_FORWARDED_FOR',
    'HTTP_X_FORWARDED',
    'HTTP_FORWARDED',
    'HTTP_CLIENT_IP',
    'HTTP_FORWARDED_FOR_IP',
    'VIA',
    'X_FORWARDED_FOR',
    'FORWARDED_FOR',
    'X_FORWARDED',
    'FORWARDED',
    'CLIENT_IP',
    'FORWARDED_FOR_IP',
    'HTTP_PROXY_CONNECTION'
);
foreach($proxy_headers as $x){
    if (isset($_SERVER[$x])) die("You are using a proxy!");
}