怎么样得到访问者的IP，并且判断是不是属于内网的？？？

function getip() {
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;
}