PHP Geocode Calculator

function distance($lat1, $lon1, $lat2, $lon2, $unit = 'M') {
  $theta = $lon1 - $lon2;
  $dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) + cos(deg2rad($lat1)) * cos(deg2rad($lat2)) *
cos(deg2rad($theta));
  $dist = acos($dist);
  $dist = rad2deg($dist);
  $dist = $dist * 60 * 1.1515;

  if ($unit == "K") {
    $dist *= 1.609344;
  } else if ($unit == "N") {
    $dist *= 0.8684;
  }

  return round($dist, 1);
}

function bearing($lat1, $lon1, $lat2, $lon2) {
  if (round($lon1, 1) == round($lon2, 1)) {
    if ($lat1 < $lat2) {
      $bearing = 0;
    } else {
      $bearing = 180;
    }
  } else {
    $dist = distance($lat1, $lon1, $lat2, $lon2, 'N');
    $arad = acos((sin(deg2rad($lat2)) - sin(deg2rad($lat1)) * cos(deg2rad($dist / 60))) / (sin(deg2rad($dist /
60)) * cos(deg2rad($lat1))));
    $bearing = $arad * 180 / pi();
    if (sin(deg2rad($lon2 - $lon1)) < 0) {
      $bearing = 360 - $bearing;
    }
  }

  $dirs = array("N","E","S","W");

  $rounded = int_round($bearing / 22.5) % 16;
  if (($rounded % 4) == 0) {
    $dir = $dirs[$rounded / 4];
  } else {
    $dir = $dirs[2 * floor(((floor($rounded / 4) + 1) % 4) / 2)];
    $dir .= $dirs[1 + 2 * floor($rounded / 8)];
    #if ($rounded % 2 == 1)
    #  $dir = $dirs[round_to_int($rounded/4) % 4] . "-" . $dir;
  }

  return $dir;
  #return $bearing;
}