2个GPS位置之间的距离PHP

Question

I am trying to display concatenated GPS locations in a string if the distance between the input location and the one on the database is lesser than 50 kms. To do this I use a function distance($lat1, $lon1, $lat2, $lon2, $unit) which has the parameters for latitude and longitudes of the two locations. This function seems to work fine in many cases but I get a NAN as output (distance between points) in the string sometimes. I do not know what is causing it whether the function of the input. Please check my code and sample input output below. PS : $date is the latitude of the input location.

function getGPS($date,$gps){

   $stringa="";
   $connx = mysql_connect($dbhost, $dbuser, $dbpass);

   if(! $connx ) {
      die('Could not connect: ' . mysql_error());
   }

   $sqlx = 'SELECT gpslat,gpslong FROM whosonline';
   mysql_select_db('revietbw_reviewitappDB');
   $retvalx = mysql_query( $sqlx, $connx );

   if(! $retvalx ) {
      die('Could not get data: ' . mysql_error());
   }

   while($row = mysql_fetch_assoc($retvalx)) {
       $glat=(float)$row['gpslat'];
       $glong=(float)$row['gpslong'];

       $dis=distance((float)$date, (float)$gps, $glat, $glong, "K");
       echo $dis;
        if($dis<100){
           $stringa = $stringa . ":" . $glat . " " . $glong;
       }

   }

   //echo "Fetched data successfully\n";

   mysql_close($connx);
  return $stringa;
 }

 function distance($lat1, $lon1, $lat2, $lon2, $unit) {

  $theta = $lon1 - $lon2;
  $dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) +  cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta));
  $dist = acos($dist);
  $dist = rad2deg($dist);
  $miles = $dist * 60 * 1.1515;
  $unit = strtoupper($unit);

  if ($unit == "K") {
      return ($miles * 1.609344);
  } else if ($unit == "N") {
      return ($miles * 0.8684);
  } else {
      return $miles;
  }
}

Sample Input : gpslong=101.1020&gpslat=11.1241 Output : NANNANNAN872.77757900898

Answer 1

The reason for NAN values was the 0 difference between the input and database GPS locations. I handled them separately.

if($dis<100 &$dis!='NAN'){
     $stringa = $stringa . ":". $unz . " " . $glat . " " . $glong;
   }

would do the job. Additionally I would also recommend to use Mysqli or pdo as its deprecated in PHP 5.5 and unsupported in higher PHP 7.