1. /**
    2.  * 根据经纬度计算两点间距离
    3.  * @param int $lat1
    4.  * @param int $lon1
    5.  * @param int $lat2
    6.  * @param int $lon2
    7.  * @param string $unit
    8.  * @return float
    9.  */
    10. public static function distance($lat1, $lon1, $lat2, $lon2, $unit = "K")
    11. {
    12.     $theta = $lon1 - $lon2;
    13.     $dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) + cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta));
    14.     $dist = acos($dist);
    15.     $dist = rad2deg($dist);
    16.     $miles = $dist * 60 * 1.1515; //此处返回值单位为英里
    17.     $unit = strtoupper($unit);
    19.     //单位转换
    20.     if ($unit == "K") {
    21.         return ($miles * 1.609344);//1英里=1.609344公里
    22.     } else if ($unit == "N") {
    23.         return ($miles * 0.8684);//1英里=0.8684海里
    24.     } else { //mi
    25.         return $miles;//英里
    26.     }
    27. }