php 获取client真实ip

<?php
/**
* 获取用户真实 IP
*
* @Author: 小熊
* @Return: string
*/
function getIP()
{
    static $realip;
    if (isset($_SERVER)){
        if (isset($_SERVER["HTTP_X_FORWARDED_FOR"])){
            $realip = $_SERVER["HTTP_X_FORWARDED_FOR"];
        } else if (isset($_SERVER["HTTP_CLIENT_IP"])) {
            $realip = $_SERVER["HTTP_CLIENT_IP"];
        } else {
            $realip = $_SERVER["REMOTE_ADDR"];
        }
    } else {
        if (getenv("HTTP_X_FORWARDED_FOR")){
            $realip = getenv("HTTP_X_FORWARDED_FOR");
        } else if (getenv("HTTP_CLIENT_IP")) {
            $realip = getenv("HTTP_CLIENT_IP");
        } else {
            $realip = getenv("REMOTE_ADDR");
        }
    }