PHP 获取访问端的IP地址

<?php
  $ip_address=getIpAddress();
  echo "$ip_address<br>";
  function getIpAddress(){
     //ip是否来自共享互联网
    if (!empty($_SERVER['HTTP_CLIENT_IP'])){
      $ip_address = $_SERVER['HTTP_CLIENT_IP'];
    }
     //ip是否来自代理
    elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])){
      $ip_address = $_SERVER['HTTP_X_FORWARDED_FOR'];
    }
     //ip是否来自远程地址
    else{
      $ip_address = $_SERVER['REMOTE_ADDR'];
    }
    return $ip_address;
  }
?>