maxmind GeoLiteCity doesn't work properly

Question

I'm using maxmind GeoLiteCity to show city name base on user IP address, it show for some of cities but not for all cities. Here's my code: I downloaded latest GeoLiteCity.dat from following link: http://dev.maxmind.com/geoip/legacy/geolite/

include("geoipcity.inc");
include("geoipregionvars.php");
$ip = $_SERVER['REMOTE_ADDR']; 
$gi = geoip_open("GeoLiteCity.dat",GEOIP_STANDARD);
$record= geoip_record_by_addr($gi,$ip);
echo 'City Name: '.$record->city . "\n";
geoip_close($gi);

how to solve it ?

Thanks