This question already has an answer here:
I'm using ipinfodb via PHP v2. ipinfodb returns 3-5% of our daily calls with CountryCode as 'RD'. Can't find RD in valid country codes. I will start logging IP's for RD returns, so far I only know that the majority of these users are on cell phone networks.
I'm using the following to call ipinfodb's API.
$sc=stream_context_create(array('http'=>array('timeout'=>5)));
$r=file_get_contents("http://api.ipinfodb.com/v2/ip_query_country.php?key=***",0,$sc);
$a=new SimpleXMLElement($r);
$country=$a->CountryCode;
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→ I did some research and didn't find a straight-up definition for "RD" but did find this in someone's code on w3lessons:
// Check if Local
if($country_code=="RD")
$country_code="US";
→ Hope that helps :p