php通过百度地图API获取输入地点经纬度，计算距离

    $address="洛阳师范学院";
    $url='http://api.map.baidu.com/geocoder/v2/?address='.$address.'&output=json&ak=5bd3d7098501b1c558d92dab30b097eb';
    $result=file_get_contents($url);
    $starend=json_decode($result,true);
	print_r($res);die;
	//Array ( [status] => 0 [result] => Array ( [location] => Array ( [lng] => 112.47368603049 [lat] => 34.683725959347 ) [precise] => 0 [confidence] => 70 [comprehension] => 0 [level] => 教育 ) )


/**
 * 计算两点之间的距离
 * @param $lng1 经度1
 * @param $lat1 纬度1
 * @param $lng2 经度2
 * @param $lat2 纬度2
 * @param int $unit m，km
 * @param int $decimal 位数
 * @return float
 */
function getDistance($lng1, $lat1, $lng2, $lat2, $unit = 2, $decimal = 2)
{

    $EARTH_RADIUS = 6370.996; // 地球半径系数
    $PI           = 3.1415926535898;

    $radLat1 = $lat1 * $PI / 180.0;
    $radLat2 = $lat2 * $PI / 180.0;

    $radLng1 = $lng1 * $PI / 180.0;
    $radLng2 = $lng2 * $PI / 180.0;

    $a = $radLat1 - $radLat2;
    $b = $radLng1 - $radLng2;

    $distance = 2 * asin(sqrt(pow(sin($a / 2), 2) + cos($radLat1) * cos($radLat2) * pow(sin($b / 2), 2)));
    $distance = $distance * $EARTH_RADIUS * 1000;

    if ($unit === 2) {
        $distance /= 1000;
    }

    return round($distance, $decimal);
}