How best to check if a user is from China and hide content?

To speed up my website in China I thought of hiding blocked services from Chinese users and wrote this and put it in functions.php

$isInChina = false; 
$ip = $_SERVER['REMOTE_ADDR']; // This will contain the ip of the request 
// This service tells me where the IP address is from and gives me more data than I need. 
$userData = json_decode(file_get_contents("http://www.geoplugin.net/json.gp?ip=".$ip)); 
if (is_Null($userData) || empty($userData) || $userData->geoplugin_countryCode == "CN")
{ 
    $isInChina = true; // Count no data as in China maybe to be paranoid. 
}

Shouldn’t I store the result in some session level variable?