PHP uses a given latitude and longitude point to make a nearby location query – the rational use of the algorithm

The implementation principle first calculates the four points of the rectangle around the point, and then uses latitude and longitude to directly match the records in the database.    //get around coordinates    public function returnsquarepoint ($lng,  $lat, $ distance = 0.5) {          $earthRadius  =  6378138;         $dlng  =  2 * asin (sin ($ distance /  (2 *  $earthRadius))  / cos (Deg2rad ($lat)));          $dlng  = rad2deg ($dlng);         $dlat  =  $distance/$earthRadius;         $dlat  = rad2deg ( $dlat);         return array (                         ' Left-top ' =>array (' lat ' = $lat  +  $dlat, ' lng ' = $lng-$dlng),      &NBsp;                  ' Right-top ' =>array (' lat ' = = $lat  +  $dlat,  ' LNG '  +  ' $dlng $lng,                          ' Left-bottom ' =>array (' lat ' = $lat  -  $dlat,  ' lng ' = $lng  - $ DLNG),                         ' Right-bottom ' =>array (' lat ' = $lat  -  $dlat,  ' lng ' = $LNG  +  $dlng)         );   }    Calculates a straight line distance of two coordinates       public function getdistance ($lat 1,  $lng 1,   $lat 2,  $lng 2) {                  $earthRadius   = 6378138; //approximate earth radius meters           //  convert to radians             $lat 1 =  ($lat 1 * pi ())  /  180;           $lng 1 =  ($lng 1 * pi ())  / 180;           $lat 2 =  ($lat 2 *  pi ())  / 180;           $lng 2 =  ($ Lng2 * pi ())  / 180;          //  Use the semi-normal vector formula    calculate          $calcLongitude with ruler gauges  =  $lng 2  -  $lng 1;           $calcLatitude  =  $lat 2  -  $lat 1;           $stepOne  = pow (sin ($ CALCLATITUDE / 2), 2)  + cos ($lat 1)  * cos ($lat 2)  * pow (sin ($calcLongitude  / 2),  2);          $stepTwo  = 2 * asin (min (1,  SQRT ($stepOne)));           $calculatedDistance  =   $earthRadius  *  $stepTwo;           return  round ($calculatedDistance);    }

PHP uses a given latitude and longitude point to make a nearby location query – the rational use of the algorithm