/**
 * 距离计算函数
 *
 * @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; 
} 
}
//用法：
echo distance(32.9697,-96.80322,29.46786,-98.53506,"k")." kilometers";
/***   来自编程之家 jb51.cc（jb51.cc）   ***/