Proper way to make PHP “POST” statements in Java (Android-Studio)

Question

I'm trying to post two strings on a PHP web server. First, I use this relevant part of my PHP script, which does work in other projects with other languages.

function open($db){
    $name = $_POST['name'];
    $pwd = $_POST['pwd'];

    // Prepare SQL statement
    $statement = $db->prepare("SELECT * FROM `table` WHERE `name`=?");
    $statement->bind_param("s", $name);
    $statement->execute();
    $result = $statement->get_result();
    $row = mysqli_fetch_assoc($result);

    if($result->num_rows > 0){
       $hashed_pwd = $row['pwd'];
     }
    else{
        echo 'No result!';
        $statement->close();
        return;
    }

    if(password_verify($pwd, $hashed_pwd)){
        echo 'Success!';
    }
    else {
      echo 'Wrong password!';
    }
    // Close SQL Statement
    $statement->close();

}

In Java, I face multiple problems. The function gets called, when pressing the “Open” button:

public void onOpenClick(View v){
    final String name = "someString";
    final String pwd = "someString";

    new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                //Add the action to the original URL
                urlString += "?action=open";

                URL url = new URL(urlString);

                HttpsURLConnection con = (HttpsURLConnection) url.openConnection();

                String info = "name=" + name + "pwd=" + pwd;
                con.setRequestMethod("POST");
                con.setDoOutput(true);
                con.getOutputStream().write(info.getBytes("UTF-8"));

                con.getInputStream();
                BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));

                answer = in.readLine();

            }catch (Exception e){
                System.out.println(e.toString());
                answer = e.toString();
            }
        }
    }).start();

}

Is using a Thread the correct way to make a PHP requests? Furthermore, I always get as answer “No result,” and if I change the echo statement in the PHP file to $name. nothing returns at all, In conclusion, the connection to my server is successful. the POST statement is not, I tried different approaches. none of them worked, If I press the button again. I do not get any response at all and answer is null or empty.

Edit

I tried adding following statements as well:

con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
con.setRequestProperty("charset", "utf-8");

And:

StringBuilder postData = new StringBuilder();

postData.append(URLEncoder.encode("name", "UTF-8"));
postData.append("=");
postData.append(URLEncoder.encode(name, "UTF-8"));

postData.append(URLEncoder.encode("pwd", "UTF-8"));
postData.append("=");
postData.append(URLEncoder.encode(pwd, "UTF-8"));

byte[] postDataBytes = postData.toString().getBytes(StandardCharsets.UTF_8);

con.setRequestMethod("POST");
con.setInstanceFollowRedirects(false);
con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
con.setRequestProperty("charset", "utf-8");
con.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
con.setDoOutput(true);
con.setUseCaches(false);

Answer 1

I had the same issue when trying to call a php server from javascript. I figured out I needed to add the Content-Type header correctly.

 'Content-Type': 'application/x-www-form-urlencoded'