PHP获取用户ip

/**
 * 获取用户ip
 * @return array|false|mixed|string
 */
function get_ip()
{
    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");
        }
    }
    return $realip;
}