PHP get remote ip address

function get_ip()
{
	$ipaddr = "Unknown";
	if ($HTTP_SERVER_VARS["HTTP_X_FORWARDED_FOR"]) {
		$ipaddr = $HTTP_SERVER_VARS["HTTP_X_FORWARDED_FOR"];
	} elseif ($HTTP_SERVER_VARS["HTTP_CLIENT_IP"]) {
		$ipaddr = $HTTP_SERVER_VARS["HTTP_CLIENT_IP"];
	} elseif ($HTTP_SERVER_VARS["REMOTE_ADDR"]) {
		$ipaddr = $HTTP_SERVER_VARS["REMOTE_ADDR"];
	} elseif (getenv("HTTP_X_FORWARDED_FOR")) {
		$ipaddr = getenv("HTTP_X_FORWARDED_FOR");
	} elseif (getenv("HTTP_CLIENT_IP")) {
		$ipaddr = getenv("HTTP_CLIENT_IP");
	} elseif (getenv("REMOTE_ADDR")) {
		$ipaddr = getenv("REMOTE_ADDR");
	}
	return $ipaddr;
}