PHP 用户地址定位

$ip = get_real_ip();
$url = "http://int.dpool.sina.com.cn/iplookup/iplookup.php?format=json&ip=$ip";
$data = file_get_contents($url);
$result = json_decode($data);
echo "城市:" . $result->city . "<br>";
print_r($result);

function get_real_ip(){
if(!empty($_SERVER['HTTP_CLIENT_IP'])){
$ip = $_SERVER['HTTP_CLIENT_IP'];
}elseif(!empty($_SERVER['HTTP_X_FORWARDED_FOR'])){
$ip= $_SERVER['HTTP_X_FORWARDED_FOR'];
}else{
$ip = $_SERVER['REMOTE_ADDR'];
}
return $ip;
}