PHP取得用户真实IP

function getIp() {
   if($_SERVER['HTTP_CLIENT_IP']) {
   $ip = $_SERVER['HTTP_CLIENT_IP'];
   } elseif ($_SERVER['HTTP_X_FORWARDED_FOR']) {
    $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
   } else {
    $ip = $_SERVER['REMOTE_ADDR'];
   }
}