Can't Get value from java to php

Question

I want to get pass the value from java to php. the example content that i want to display in php is:

"2019-11-28 13:06:43 Latitude: 13.54, Longitude: 129.0"

error that I'm getting is:

"Notice: Undefined index: latitude in C:\xampp\htdocs\location.php on line 7"

"Notice: Undefined index: longitude in C:\xampp\htdocs\location.php on line 7"

JAVA

 public class PostServer extends AsyncTask<String, String, String>
{
    private HashMap<String, Double> parameters;
    private int min;

    public PostServer(double lat, double lon, int mins) {
        parameters = new HashMap<>();
        parameters.put("latitude", lat);
        parameters.put("longitude", lon);
        min = mins;

    }

    @Override
    protected String doInBackground(String... strings) {
        StringBuilder postParameters = new StringBuilder();
        boolean first = true;
        try{
            URL url = new URL("http://172.17.9.47/location.php");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");

            for(Map.Entry<String, Double> postParams : parameters.entrySet()){
                if (first) {
                    first = false;
                }
                else {
                    postParameters.append("&");

                    postParameters.append(URLEncoder.encode(postParams.getKey(), "UTF-8"));
                    postParameters.append("=");
                    postParameters.append(URLEncoder.encode(String.valueOf(postParams.getValue()), "UTF-8"));
                }
            }
            postParameters.append("&min=");
            postParameters.append(min);


            OutputStreamWriter oStream = new OutputStreamWriter(connection.getOutputStream());
            oStream.write(postParameters.toString());
            oStream.flush();
            oStream.close();

            BufferedReader bReader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            StringBuilder result = new StringBuilder();
            String line;
            while ((line = bReader.readLine()) != null){
                result.append(line);
            }
            return result.toString();
        } catch (IOException e){
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(String s) {
        sendBroadcast(" Longitude: "+lon +" Latitude: " + lat );
        super.onPostExecute(s);
    }
}

PHP

<?php
$myfile = fopen("Task5.2/location.txt", "w");

fwrite($myfile, "testing");
fclose($myfile); 

if( $_POST["latitude"] || $_POST["longitude"] ) {
date_default_timezone_set("Singapore");
  echo date("Y-m-d h:i:sa"). "\t";
  echo "Latitude: ". $_POST['latitude']. ",\t";
  echo "Longitude: ". $_POST['longitude'];
}

?>