geohash
What's GeoHash
LINK: http://en.wikipedia.org/wiki/Geohash
Usage
use Cevin\Geohash;
$length = 6;
$geohash = new Geohash();
$hash = substr($geohash->encode('latitude','longitude'), 0, $length);
$box = $geohash->neighbors($hash);
$box[] = $hash;
$in_str = "'".implode("','", $box)."'";
// PHP
// $sql = "SELECT FROM `table` WHERE LEFT(geohash, {$length}) IN ($in_str)";
// echo $sql;
// OUTPUT
// SELECT FROM `table` WHERE LEFT(geohash, 6) IN ('xxxxxx','aaaaaa', ......)