Radius PHP

date_default_timezone_set('Asia/Jakarta');

            function distance($lat1, $lon1, $lat2, $lon2, $unit) {
                if (($lat1 == $lat2) && ($lon1 == $lon2)) {
                    return 0;
                }else{
                    $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;
                    }
                }
            }

            $latitude       = -7.323501;
            $longitude      = 112.741151;
            $jarak_max      = 40;
            $lat2           = -7.324446;
            $lon2           = 112.746595;
            $lat1           = $latitude;
            $lon1           = $longitude;
            $kilometer      = distance($lat1,$lon1,$lat2,$lon2,"K");
            $meter          = floor($kilometer*1000);
            $work_location  = "Pusat";
            $timestamp      = date('Y-m-d H:i:s');

            if(($meter>$jarak_max)):
                $data[0]['value']       = 2;
                $data[0]['messages']    = 'Gagal - Melewati Maksimum Jarak Absen !';
                $data[0]['waktuserver'] = $timestamp;
                $data[0]['jml_dist']    = $meter;
                echo json_encode($data);
            else:
                $data[0]['value']       = 1;
                $data[0]['messages']    = 'Berhasil - Anda diperbolehkan absen !';
                $data[0]['waktuserver'] = $timestamp;
                $data[0]['jml_dist']    = $meter;
                echo json_encode($data);
            endif;