PHP algorithm calculates the distance between map coordinates of Baidu star small stack

/** calculate the distance between two coordinates (m) * @param float $fP 1Lat starting point (latitude) * @param float $fP 1Lon Start (longitude) * @param float $fP 2Lat end point (latitude) * @param Float $fP 2Lon end point (longitude) * @return int*/functionDistancebetween ($fP 1Lat,$fP 1Lon,$fP 2Lat,$fP 2Lon){    $fEARTH _radius= 6378137; //Angle converted to radians    $fRadLon 1=Deg2rad($fP 1Lon); $fRadLon 2=Deg2rad($fP 2Lon); $fRadLat 1=Deg2rad($fP 1Lat); $fRadLat 2=Deg2rad($fP 2Lat); //calculate the difference between latitude and longitude    $fD 1=ABS($fRadLat 1-$fRadLat 2); $fD 2=ABS($fRadLon 1-$fRadLon 2); //Distance Calculation    $fP=POW(Sin($fD 1/2), 2) +Cos($fRadLat 1) *Cos($fRadLat 2) *POW(Sin($fD 2/2), 2); return intval($fEARTH _radius* 2 *ASIN(sqrt($fP)) + 0.5);}/** * Baidu coordinate system converted to standard GPS sitting system * @param float $lnglat coordinates (such as: 106.426, 29.553404) * @return The standard GPS value after string conversion:*/functionBD09LLTOWGS84 ($lnglat){//Longitude, Latitude    $lnglat=Explode(‘,‘,$lnglat); List($x,$y) =$lnglat; $Baidu _server= "http://api.map.baidu.com/ag/coord/convert?from=0&to=4&x={$x}&y={$y}"; $result= @file_get_contents($Baidu _server); $json= Json_decode ($result); if($json->error = = 0){        $BX=Base64_decode($json-x); $by=Base64_decode($json-y); $GPS _x= 2 *$x-$BX; $GPS _y= 2 *$y-$by; return $GPS _x.‘,‘.$GPS _y;//Longitude, Latitude}Else        return $lnglat;}

Cited by: http://www.jb51.net/article/59658.htm

PHP algorithm calculates the distance between map coordinates of Baidu star small stack