public class RegisterFragment extends Fragment {
private SessionManager session;
EditText etEmail, etUsername, etPassword,etConfirmPassword;
String email, userName, userPass,confirmPassword;
Button registerButton;

public RegisterFragment() {
    // Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View v = inflater.inflate(R.layout.fragment_register, container, false);
    Toolbar myToolbar = (Toolbar) v.findViewById(R.id.toolbar);
    ((AppCompatActivity)getActivity()).setSupportActionBar(myToolbar);
    setHasOptionsMenu(true);

    etEmail = (EditText)v.findViewById(R.id.name);
    etUsername = (EditText)v.findViewById(R.id.user_name);
    etPassword = (EditText)v.findViewById(R.id.user_pass);
    etConfirmPassword = (EditText)v.findViewById(R.id.confirm_pass);
    registerButton = (Button)v.findViewById(R.id.registerBtn);
    // Session manager
    // Session manager
    session = new SessionManager(getActivity());

    if (session.isLoggedIn()) {
        // User ites already logged in. Take him to main activity
        Intent intent = new Intent(getActivity(), Welcome.class);
        startActivity(intent);

    }
    registerButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            email = etEmail.getText().toString();
            userName = etUsername.getText().toString();
            userPass = etPassword.getText().toString();
            confirmPassword = etConfirmPassword.getText().toString();

            if(userPass.equals(confirmPassword)){

                registerUser(email, userName, userPass, confirmPassword);

            }else{

                Toast.makeText(getActivity(),"Passwords don't match",Toast.LENGTH_SHORT).show();
            }
        }
    });

    return v;
}
private void registerUser(final String email, final String userName,
                          final String password,final String confirmPassword) {

    String tag_string_req = "req_register";

    StringRequest strReq = new StringRequest(Request.Method.POST,
            Config.URL_REGISTER, new Response.Listener<String>() {

        @Override
        public void onResponse(String response) {
            Log.d("Response", "Register Response: " + response.toString());

            try {
                JSONObject jsonObject = new JSONObject(response);
                if (jsonObject.getString("result").equals("success")) {

                    Toast.makeText(getActivity(),jsonObject.getString("message"), Toast.LENGTH_LONG).show();

                    SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(getActivity());
                    SharedPreferences.Editor editor = settings.edit();
                    //editor.putString("id","");
                    editor.putString("email", email);
                    editor.putString("user_name", userName);
                    editor.putString("user_pass", password);
                    editor.putString("confirm_pass", confirmPassword);
                }

                else if (jsonObject.getString("result").equals("fail")) {
                    Toast.makeText(getActivity(),jsonObject.getString("message"), Toast.LENGTH_LONG).show();
                }
            }catch(JSONException e){
                e.printStackTrace();
            }
        }
    }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
            Log.e("Error", "Registration Error: " + error.getMessage());
            Toast.makeText(getActivity(),
                    error.getMessage(), Toast.LENGTH_LONG).show();
        }
    }) {
        @Override
        protected Map<String, String> getParams() {
            // Posting params to register url
            Map<String, String> params = new HashMap<String, String>();
            //params.put("id","");
            params.put("email", email);
            params.put("user_name", userName);
            params.put("user_pass", password);
            params.put("confirm_pass", confirmPassword);
            return params;
        }
    };
    // Adding request to request queue
    AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
    }
}

<?php
   session_start();
   require "init.php";
   header('Content-type: application/json');
   $id = $_POST['id'];
   $email = $_POST['email'];
   $user_name = $_POST['user_name'];

   $user_pass = $_POST['user_pass'];
   $passwordEncrypted = sha1($user_pass);

   $confirmPass = $_POST['confirm_pass'];
   $confPasswordEncrypted = sha1($confirmPass);

   $msg = "Congratulations. You are now registered to the most amazing app
   ever!";

        if(!filter_var($email, FILTER_VALIDATE_EMAIL)){


            $don = array('result' =>"fail","message"=>"Please enter a valid email");

        }



if($email && $user_name && $user_pass && $confirmPass && filter_var($email, FILTER_VALIDATE_EMAIL)){


    $sql_query = "select * from user_info WHERE email  ='".mysqli_real_escape_string($con, $email)."' or user_name
    ='".mysqli_real_escape_string($con, $user_name)."'";

    $result = mysqli_query($con, $sql_query);

    $results = mysqli_num_rows($result);

    if ($results){
        $don = array('result' =>"fail","message"=>"Email or username exists.");
    }else{

        $sql_query = "insert into user_info values('$id','$email','$user_name','$passwordEncrypted','$confPasswordEncrypted');";

        if(mysqli_query($con,$sql_query)){
            $_SESSION['id'] = mysqli_insert_id($con);
            $don = array('result' =>"success","message"=>"Successfully
           registered!Well done");
            mail($email,"Well done. You are registered to my sample app!",$msg);

        }
    }
}else if(!$email){


        $don = array('result' =>"fail","message"=>"Please enter a valid email");


    }else if(!$user_name){

        $don = array('result' =>"fail","message"=>"Please enter your username");

    }else if(!$user_pass){

        $don = array('result' =>"fail","message"=>"Please enter a password");

    }else if(!confirmPass){

        $don = array('result' =>"fail","message"=>"Please confirm your password");

  }
  echo json_encode($don);

CREATE TABLE IF NOT EXISTS `ratingplayerstable ` (
`player_id` int(10) NOT NULL AUTO_INCREMENT,
`player` text NOT NULL,
`rating` text NOT NULL,
`User_Id`int(10) NOT NULL,
 PRIMARY KEY (`player_id`),
 FOREIGN KEY (User_Id) REFERENCES user_info(id)

user_info table.
         ------------------------------------------------
         |   id    | NOT NULL AUTO INCREMENT PRIMARY KEY|
         ------------------------------------------------
         |user_name|              TEXT                  |
         ------------------------------------------------
         |user_pass|              TEXT                  |
         ------------------------------------------------
         |conf_pass|              TEXT                  |
         ------------------------------------------------
         |  email  |              TEXT                  |
         ------------------------------------------------

private void ratingPlayer(final String player, final String rating,final String UserId) {

    String tag_string_req = "req_register";

    StringRequest strReq = new StringRequest(Request.Method.POST,
            URL.URL_BEST_PLAYERS, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            Log.d("Response", "Best player response: " + response.toString());

            try {
                JSONObject jsonObject = new JSONObject(response);
                if (jsonObject.getString("result").equals("success")) {
                    Toast.makeText(getApplicationContext(), jsonObject.getString("message"), Toast.LENGTH_LONG).show();
                } else if (jsonObject.getString("result").equals("fail")) {
                    Toast.makeText(getApplicationContext(), jsonObject.getString("message"), Toast.LENGTH_LONG).show();
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
            Log.e("Error", "Registration Error: " + error.getMessage());
            Toast.makeText(getApplicationContext(),
                    error.getMessage(), Toast.LENGTH_LONG).show();

        }
    }) {
        @Override
        protected Map<String, String> getParams() {
            // Posting params to register urls
            Map<String, String> params = new HashMap<String, String>();
            params.put("player_id", "");
            params.put("User_Id", UserId);
            params.put("player", player);
            params.put("rating", rating);
            return params;
        }
    };
    // Adding request to request queue
    AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
  }

<?php
  require "init.php";
  header('Content-type: application/json');

  error_reporting(E_ALL);
  ini_set("display_errors", 1);

  $id = isset($_POST['player_id']);
  $user_id = isset($_POST['user_id']);
  $best_player = isset($_POST['player']);
  $rate = isset($_POST['rate']);

  if($id && $user_id && $best_player && $rate){

    $sql_query = "insert into rating_players_table
    values('$id','$bestplayer','$rate','$user_id');";

    if(mysqli_query($con,$sql_query)){
        $_SESSION['user_id'] = mysqli_insert_id($con);
        $don = array('result' =>"success","message"=>"Επιτυχής πρόσθεση
    παίχτη");
    }
 }if(!$best_player){

        $don = array('result' =>"fail","message"=>"Insert player name");

    }else if(!$rate){

        $don = array('result' =>"fail","message"=>"Rate player");

    }
   echo json_encode($don,JSON_UNESCAPED_UNICODE);

  ?>