[Leszek]

You could try this:

<?php 

// checking IP
function IP_prawdziwe(){ 

if ($_SERVER['HTTP_X_FORWARDED_FOR']) { 
    $ip_prawdziwe = $_SERVER['HTTP_X_FORWARDED_FOR']; 
} 
else { 
  $ip_prawdziwe = $_SERVER['REMOTE_ADDR']; 
} 

return $ip_prawdziwe; 
} 

?>

and read the IP:

<?php 
$ip = IP_prawdziwe(); 
echo IP_prawdziwe(); 
?>

It works but it doesn't always have to depending on the proxy.