Simple antispammer filtering

I'm sharing it just in case it can come in handy to other people. That is the neatest anti-spammer filter I found to this day. Four lines, no calls for anything else, no problems, no uploading stuff, can be used absolutely anywhere.

$xml_string = file_get_contents('http://www.stopforumspam.com/api?ip='.$gduserip);
        $xml = new SimpleXMLElement($xml_string);
        if($xml->appears == 'yes'){
// or, kinder,       if($xml->appears == 'yes' and (substr($xml, -1) > 4)){
// whatever the fuck I want from there. Return 0; die(), file_put_contents to a log.txt. }