How to Submit POST Data from an Android App to a PHP Script?

public class CallAPI extends AsyncTask<String, String, String> {
    // Optionally set context variables here

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {
        String urlString = params[0]; // URL to invoke
        String data = params[1]; // Data to transmit

        OutputStream out = null;
        try {
            URL url = new URL(urlString);
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            out = new BufferedOutputStream(urlConnection.getOutputStream());

            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, "UTF-8"));
            writer.write(data);
            writer.flush();
            writer.close();
            out.close();

            urlConnection.connect();
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }

        return null; // Modify this to process the response from the PHP script
    }
}