php利用百度api计算两地距离的代码

http://developer.baidu.com/map/index.php?title=webapi/ip-api

/**  
* @desc 根据两点间的经纬度计算距离  
* @param float $lat 纬度值  
* @param float $lng 经度值  
*/ 
function getDistance($lat1, $lng1, $lat2, $lng2)  
{
$earthRadius = 6367000; //approximate radius of earth in meters  
$lat1 = ($lat1 * pi() ) / 180;  
$lng1 = ($lng1 * pi() ) / 180;  
$lat2 = ($lat2 * pi() ) / 180;  
$lng2 = ($lng2 * pi() ) / 180;  
$calcLongitude = $lng2 - $lng1;  
$calcLatitude = $lat2 - $lat1;  
$stepOne = pow(sin($calcLatitude / 2), 2) + cos($lat1) * cos($lat2) * pow(sin($calcLongitude / 2), 2);  
$stepTwo = 2 * asin(min(1, sqrt($stepOne)));  
$calculatedDistance = $earthRadius * $stepTwo;  
return round($calculatedDistance);  
}