PHP从android应用程序中将空白行插入mysql表

Question

I am inserting json data from my android app in my device into xampp server in my computer using POST. It simply inserts row with empty column. When I enter the column from my browser using GET it converts it to numbers only eventhough the data is mix of numbers and letters. The type of the table column is varbinary. I entered 'crap' from my browser and it was inserted as '63726170' in the table. I am puzzled by this. Here is the PHP code that inserts the data.

if (isset($_POST)){
    //sanitize the input
    filter_var_array($_POST);
    $ri=$_POST['regID'];
    $id=json_decode($ri);
    //$decoid= $id->regID;
    if(is_array($id)){
    foreach ($id as $key=>$value){
        $fu=$id[$key];
        };
    }
    try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    // set the PDO error mode to exception
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $sql = "INSERT INTO regids (regID)
    VALUES ('$fu')";
    // use exec() because no results are returned
    $conn->exec($sql);
    echo "New record created successfully";
        }
    catch(PDOException $e)
    {
    echo $sql . "<br>" . $e->getMessage();
    }
   }else{
        echo "Error executing query!!!";
    }    
    $conn = null;

I am adding my android code that is sending the data to the server

URL url;
                    HttpURLConnection urlConn;
                    DataOutputStream printout;
                    url = new URL ("myurlhere");
                    urlConn = (HttpURLConnection)url.openConnection();
                    urlConn.setDoInput (true);
                    urlConn.setDoOutput (true);
                    urlConn.setUseCaches (false);
                    urlConn.setRequestProperty("Content-Type","application/json");   
                    urlConn.setRequestProperty("Accept", "application/json");
                    urlConn.setRequestMethod("POST");
                    urlConn.connect();

                    /*List<NameValuePair> params = new ArrayList<NameValuePair>();
                    params.add(new BasicNameValuePair("regID", result));*/
                    String result = args.toString();
                    try{
                    //Create JSONObject here
                    JSONObject jsonParam = new JSONObject();
                    jsonParam.put("regID", result);
                    String postData="json="+jsonParam.toString();


                    // Send POST output.
                    printout = new DataOutputStream(urlConn.getOutputStream ());
                    printout.writeUTF(URLEncoder.encode(jsonParam.toString(),"UTF-8"));
                    Log.i("NOTIFICATION", "Data Sent");
                    printout.flush ();
                    printout.close ();

                    OutputStreamWriter os = new OutputStreamWriter(urlConn.getOutputStream(), "UTF-8");
                    os.write(postData);
                    Log.i("NOTIFICATION", "Data Sent");



                    BufferedReader reader = new BufferedReader(new InputStreamReader(urlConn.getInputStream())); 
                    String msg=""; 
                    String line = ""; 
                    while ((line = reader.readLine()) != null) {
                        msg += line; } 
                    Log.i("msg=",""+msg);

                    os.close();