/**
 * 计算距离
 *
 * @param 
 * @author 编程之家 jb51.cc jb51.cc
 **/
function distance($lat1,$lon1,$lat2,$lon2,$unit) {
  $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);
  $miles = $dist * 60 * 1.1515;
  $unit = strtoupper($unit);
  if ($unit == "K") {
    return ($miles * 1.609344);
  } else if ($unit == "N") {
      return ($miles * 0.8684);
    } else {
        return $miles;
      }
}
echo distance(32.9697,-96.80322,29.46786,-98.53506,"k")." kilometers";


/***   来自编程之家 jb51.cc（jb51.cc）   ***/