PHP를 사용하여 IP 주소를 얻는 방법

<?php  
$ip = $_SERVER["REMOTE_ADDR"];
echo $ip;
?>

<?php 
$ip = ($_SERVER["HTTP_VIA"]) ? $_SERVER["HTTP_X_FORWARDED_FOR"] : $_SERVER["REMOTE_ADDR"];
$ip = ($ip) ? $ip : $_SERVER["REMOTE_ADDR"];
echo $ip;
?>

<?php
if(getenv(&#39;HTTP_CLIENT_IP&#39;)) {
  $onlineip = getenv(&#39;HTTP_CLIENT_IP&#39;);} elseif(getenv(&#39;HTTP_X_FORWARDED_FOR&#39;)) {
  $onlineip = getenv(&#39;HTTP_X_FORWARDED_FOR&#39;);} elseif(getenv(&#39;REMOTE_ADDR&#39;)) {
  $onlineip = getenv(&#39;REMOTE_ADDR&#39;);} else {
  $onlineip = $HTTP_SERVER_VARS[&#39;REMOTE_ADDR&#39;];}echo $onlineip;
?>