Radius search

radius.php

<?php

/**
 * Simple helper to fetch the bounding boxes
 * for a point on the map (lat,lng) by radius. 
 * 
 * @param double $lat Latitude
 * @param double $lng Longitude
 * @param int $radius Radius in km
 * @return array
 */
function getBoundingBox($lat, $lng, $radius) {

  $earthRadius = 6371;

  $maxLat = $lat + rad2deg($radius / $earthRadius);
  $minLat = $lat - rad2deg($radius / $earthRadius);
  $maxLng = $lng + rad2deg($radius / $earthRadius/cos(deg2rad($lat)));
  $minLng = $lng - rad2deg($radius / $earthRadius/cos(deg2rad($lat)));
 
  return array(
    'minLat' => $minLat,
    'maxLat' => $maxLat,
    'minLng' => $minLng,
    'maxLng' => $maxLng,
    'center' => array('lat' => $lat,    'lng' => $lng),
    'nw'     => array('lat' => $maxLat, 'lng' => $minLng),
    'ne'     => array('lat' => $maxLat, 'lng' => $maxLng),
    'sw'     => array('lat' => $minLat, 'lng' => $minLng),
    'se'     => array('lat' => $minLat, 'lng' => $maxLng),
  );

}

// search in all visible children of the current page
// each subpage must have a lat (Latitude) field and a lng (Longitude) field 
// in order to make the search work. 
$entries = $page->children()->visible();

// set the desired radius
$radius = 25; // 25 km

// get the min and max lat and the min and max lng
$coords = getBoundingBox($lat = 49.5004256, $lng = 8.5020751, $radius);  

// filter entries with a custom filter
$entries = $entries->filter(function($retailer) use($coords) {

  if(doubleval($retailer->lat()->value) >= $coords['minLat'] and 
     doubleval($retailer->lat()->value) <= $coords['maxLat'] and
     doubleval($retailer->lng()->value) >= $coords['minLng'] and
     doubleval($retailer->lng()->value) <= $coords['maxLng']) {
    return true;
  } else {
    return false;
  }

});

// do something with the filtered entries here.