Geocoder GeoIP provider that works with the default GeoIP database. This means that you can use this provider to determine the country of a visitor simply by installing php5-geoip (or equivalent package).
$geocoder = new \Geocoder\Geocoder();
$geocoder->registerProvider(new \GeoipCountryProvider\GeoipCountryProvider());
var_dump($geocoder->geocode('8.8.8.8'));
// Output:
//
// object(Geocoder\Result\Geocoded)[55]
// protected 'latitude' => int 0
// protected 'longitude' => int 0
// protected 'bounds' => null
// protected 'streetNumber' => null
// protected 'streetName' => null
// protected 'cityDistrict' => null
// protected 'city' => null
// protected 'zipcode' => null
// protected 'county' => null
// protected 'countyCode' => null
// protected 'region' => null
// protected 'regionCode' => null
// protected 'country' => string 'United States' (length=13)
// protected 'countryCode' => string 'US' (length=2)
// protected 'timezone' => null