Determining if public proxies are anonymous
<?php
foreach (getallheaders() as $name => $value) {
    echo "$name: $valuen";
}
?>

<?php
$headers = array();
foreach($_SERVER as $key => $value) {
    if(strpos($key, 'HTTP_') === 0) {
        $headers[str_replace(' ', '-', ucwords(str_replace('_', ' ', strtolower(substr($key, 5)))))] = $value;
        echo $value;
    }
}
?>