Sorry: Also quite late to the party. :-)
With access to the Maxmind GeoLite2 City Database you can optain latitude and longitude of your mirrors and your visitors and redirect accordingly.
I've created a small script that tells you which server it would redirect you too based on the nearest server to you. Instead of the echo statements you would just do a header("Location: .....); redirect.
Here is the complete exmaple:
<?php
/**
* Credit for the function: https://stackoverflow.com/a/10054282
* Calculates the great-circle distance between two points, with
* the Vincenty formula.
* @param float $latitudeFrom Latitude of start point in [deg decimal]
* @param float $longitudeFrom Longitude of start point in [deg decimal]
* @param float $latitudeTo Latitude of target point in [deg decimal]
* @param float $longitudeTo Longitude of target point in [deg decimal]
* @param float $earthRadius Mean earth radius in [m]
* @return float Distance between points in [m] (same as earthRadius)
*/
function vincentyGreatCircleDistance(
$latitudeFrom, $longitudeFrom, $latitudeTo, $longitudeTo, $earthRadius = 6371000)
{
// convert from degrees to radians
$latFrom = deg2rad($latitudeFrom);
$lonFrom = deg2rad($longitudeFrom);
$latTo = deg2rad($latitudeTo);
$lonTo = deg2rad($longitudeTo);
$lonDelta = $lonTo - $lonFrom;
$a = pow(cos($latTo) * sin($lonDelta), 2) +
pow(cos($latFrom) * sin($latTo) - sin($latFrom) * cos($latTo) * cos($lonDelta), 2);
$b = sin($latFrom) * sin($latTo) + cos($latFrom) * cos($latTo) * cos($lonDelta);
$angle = atan2(sqrt($a), $b);
return $angle * $earthRadius;
}
$download_servers = array( 0 => array( 'hostname' => "ftp.bu.edu",
'longitude' => null,
'latitude' => null,
'city' => null,
'distance' => null),
1 => array( 'hostname' => "www.softlayer.com",
'longitude' => null,
'latitude' => null,
'city' => null,
'distance' => null),
2 => array( 'hostname' => "download.nust.na",
'longitude' => null,
'latitude' => null,
'city' => null,
'distance' => null),
3 => array( 'hostname' => "mirror.isoc.org.il",
'longitude' => null,
'latitude' => null,
'city' => null,
'distance' => null),
4 => array( 'hostname' => "download.nus.edu.sg",
'longitude' => null,
'latitude' => null,
'city' => null,
'distance' => null),
5 => array( 'hostname' => "mirror.yandex.ru",
'longitude' => null,
'latitude' => null,
'city' => null,
'distance' => null),
6 => array( 'hostname' => "ftp.iij.ad.jp",
'longitude' => null,
'latitude' => null,
'city' => null,
'distance' => null)
);
require_once( __DIR__ . "/maxmind/geoip2.phar");
use GeoIp2\Database\Reader;
// City DB
$reader = new Reader( __DIR__ . '/maxmind/GeoLite2-City.mmdb');
$record = $reader->city($_SERVER['REMOTE_ADDR']);
$i = 0;
foreach ($download_servers as $server) {
//$record2 = $reader->city($server['ip']);
$record2 = $reader->city(gethostbyname($server['hostname']));
if (!isset($download_servers[$i]['longitude'])) {
$download_servers[$i]['longitude'] = $record2->location->longitude;
$download_servers[$i]['latitude'] = $record2->location->latitude;
}
$download_servers[$i]['city'] = $record2->city->name;
$download_servers[$i]['distance'] = vincentyGreatCircleDistance( $record->location->latitude, $record->location->longitude,
$download_servers[$i]['latitude'], $download_servers[$i]['longitude']);
$i++;
}
$dists = array_column($download_servers, 'distance');
$min = array_search(min($dists), $dists, true);
echo "Nearest download server is: " . $download_servers[$min]['hostname'] . " in " . $download_servers[$min]['city'] . "<br>";
echo "Distance to you (" . $record->city->name . ") is: " . $download_servers[$min]['distance'] / 1000 . " km";
