PHP 获取IP地址

<?php
/**
 * 客户端IP，
 * @return array|false|string
 */
function getIP(){
    if (getenv("HTTP_CLIENT_IP"))
        $ip = getenv("HTTP_CLIENT_IP");
    else if(getenv("HTTP_X_FORWARDED_FOR"))
        $ip = getenv("HTTP_X_FORWARDED_FOR");
    else if(getenv("REMOTE_ADDR"))
        $ip = getenv("REMOTE_ADDR");
    else $ip = "Unknow";
    if(preg_match('/^((?:(?:25[0-5]|2[0-4]\d|((1\d{2})|([1-9]?\d)))\.){3}(?:25[0-5]|2[0-4]\d|((1\d{2})|([1 -9]?\d))))$/', $ip))
        return $ip;
    else
        return '';
}
/**
 * 服务器端IP
 * @return string
 */
function serverIP(){
    return gethostbyname($_SERVER["SERVER_NAME"]);
}