<?PHP
define('EARTH_RADIUS',6370.6935);
function vicinity($lng,$lat,$distance = 0.5) {
//$distance = 0.5; // 单位 10KM
$radius = EARTH_RADIUS;
$dlng = rad2deg(2*asin(sin($distance/(2*$radius))/cos($lat)));
$dlat = rad2deg($distance*10/$radius);
$lng_left = round($lng - $dlng,6);
$lng_right = round($lng + $dlng,6);
$lat_top = round($lat + $dlat,6);
$lat_bottom = round($lat - $dlat,6);
return array('lng'=> array('left'=> $lng_left,'right'=> $lng_right),'lat'=> array('top'=> $lat_top,'bottom'=> $lat_bottom));
}
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