PHP method to obtain IP

<?php
//获取IP
function get_ip() {
        if (isset($_SERVER)) {
                if (isset($_SERVER[HTTP_X_FORWARDED_FOR])) {
                        $realip = $_SERVER[HTTP_X_FORWARDED_FOR];
                } elseif (isset($_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");
                } elseif (getenv("HTTP_CLIENT_IP")) {
                        $realip = getenv("HTTP_CLIENT_IP");
                } else {
                        $realip = getenv("REMOTE_ADDR");
                }
        }
        return $realip;
}
?>