How to use CURL to forge IP source in PHP

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "http://localhost/2.php");
curl_setopt($ch, CURLOPT_HTTPHEADER, array('X-FORWARDED-FOR:8.8.8.8', 'CLIENT-IP:8.8.8.8'));//IP
curl_setopt($ch, CURLOPT_REFERER, "http://bbs.it-home.org/ ");   //来路
curl_setopt($ch, CURLOPT_HEADER, 1);
$out = curl_exec($ch);
curl_close($ch);

2.文件 2.php

function getClientIp() {
    if (!empty($_SERVER["HTTP_CLIENT_IP"]))
        $ip = $_SERVER["HTTP_CLIENT_IP"];
    else if (!empty($_SERVER["HTTP_X_FORWARDED_FOR"]))
        $ip = $_SERVER["HTTP_X_FORWARDED_FOR"];
    else if (!empty($_SERVER["REMOTE_ADDR"]))
        $ip = $_SERVER["REMOTE_ADDR"];
    else
        $ip = "err";
    return $ip;
}
echo "IP: " . getClientIp() . "";
echo "referer: " . $_SERVER["HTTP_REFERER"];

用1.php 请求 2.php，输出结果： IP：8.8.8.8 referer:http://bbs.it-home.org

伪造成功。