Error E / JSON Parser: Error parsing data org.json.JSONException: Value br of type java.lang.String can not be converted to JSONObject

Very good to all and first of all thank you for reading this

I've been pulling my hair for a couple of days because I try to create an application in android studio, but I can not get past the attempt to create the user account, I use PHP, wamp and android studio but there's no way, this is the error that comes to me:

E/JSON Parser: Error parsing data org.json.JSONException: Value <br of type java.lang.String cannot be converted to JSONObject
V/params: [nombre=afafa, clave=afafa, correo=afa, pregunta=1 ¿En que ciudad nació?, respuesta=1313, informacion=1]
E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #2
              Process: com.example.bruno.thulin, PID: 27878
              java.lang.RuntimeException: An error occurred while executing doInBackground()
                  at android.os.AsyncTask$3.done(AsyncTask.java:354)
                  at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
                  at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
                  at java.util.concurrent.FutureTask.run(FutureTask.java:271)
                  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
                  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
                  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
                  at java.lang.Thread.run(Thread.java:764)
               Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String org.json.JSONObject.toString()' on a null object reference
                  at com.example.bruno.thulin.inicio.CrearCuenta$CrearNuevoUsuario.doInBackground(CrearCuenta.java:215)
                  at com.example.bruno.thulin.inicio.CrearCuenta$CrearNuevoUsuario.doInBackground(CrearCuenta.java:164)
                  at android.os.AsyncTask$2.call(AsyncTask.java:333)
                  at java.util.concurrent.FutureTask.run(FutureTask.java:266)
                  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245) 
                  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) 
                  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) 
                  at java.lang.Thread.run(Thread.java:764) 

I have tried it in a thousand ways but I can not find the solution, this is my code:

the php to create user:

create_user.php

<?php

/*
 *Este código creará los usuarios nuevos
 */ 

// Array para la respuesta del JSON

 $response = array();

// comprobación de los campos requeridos

 if (isset($_POST['nombre']) && isset($_POST['clave']) && isset($_POST['correo']) && isset($_POST['pregunta']) && isset($_POST['respuesta'])) {

 $nombre = $_POST['nombre'];
 $clave = $_POST['clave'];
 $correo = $_POST['correo'];
 $pregunta = $_POST['pregunta'];
 $respuesta = $_POST['respuesta'];
 $informacion = $_POST['informacion'];

 // se incluye la clase de db connect

 include('db_connect.php');

 // Conectando con la bd

 $db = new DB_CONNECT();

 // mysql insertando nueva fila

 $link = mysqli_connect("localhost","thulin","","thulin");

 $result = mysqli_query($link,'INSERT INTO usuario (nombre, clave, correo, pregunta, respuesta, informacion) VALUES ($nombre, $clave, $correo, $pregunta, $respuesta, $informacion)');

 // Comprobación de si la fila se ha insertado o no

 if ($result) {
    // successfully inserted into database
    $response["success"] = 1;
    $response["message"] = "Cuenta creada con exito.";

    // echoing JSON response
    echo json_encode($response);
} else {
    // failed to insert row
    $response["success"] = 0;
    $response["message"] = "Ha ocurrido un error.";

    // echoing JSON response
    echo json_encode($response);
    }
} else {
// required field is missing
$response["success"] = 0;
$response["message"] = "Falta algún campo";

// echoing JSON response
echo json_encode($response);
}
?>

And this is the class in Android Studio that calls the php and should create the account:

Create Account.java

package com.example.bruno.thulin.inicio;

import android.annotation.SuppressLint;
import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.Typeface;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

import com.example.bruno.thulin.R;
import com.example.bruno.thulin.json.JSONparser;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.net.URL;
import java.util.ArrayList;
import java.util.List;

public class CrearCuenta extends AppCompatActivity {

private EditText etNombre, etPassword, etCorreo, etRespuesta;
private Button btnCrearCuenta;
private CheckBox informacion;
private boolean pregunta;
private ProgressDialog pDialog;
private JSONparser jsonParser = new JSONparser();
private static String url_crear_usuario;
private static final String TAG_SUCCESS = "success";
private String nombre;
private String password;
private String correo;
private String eleccion;
private String respuesta;
private String infostring;
private int info;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_crear_cuenta);


    final Spinner dropdown = findViewById(R.id.spinnercreacioncuenta);
    etNombre = findViewById(R.id.etnombrecreacioncuenta);
    etPassword = findViewById(R.id.etpasswordcreacioncuenta);
    etCorreo = findViewById(R.id.etcorreocreacioncuenta);
    etRespuesta = findViewById(R.id.etrespuestacreacioncuenta);
    btnCrearCuenta = findViewById(R.id.btncrearcuenta);
    informacion = findViewById(R.id.checkinfocreacioncuenta);
    url_crear_usuario = "http://192.168.8.100/thulin/crear_usuario.php";

    final Typeface type = Typeface.createFromAsset(getAssets(), "fonts/doriel.otf");

    final String[] items = new String[]{"1.- ¿En que ciudad nació?", "2.- ¿Cual es el nombre de su primer amor?", "3.- ¿Como se llama su pareja actual?", "4.- ¿De que raza es su perro?", "5.- ¿Como se llama su perro?", "6.- ¿Como se llamaba su primer instituto?", "7.- ¿Como se llama su madre?", "8.- ¿Como se llama su padre?"};

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.my_spinner_style, items) {

        public View getView(int position, View convertView, ViewGroup parent) {

            View v = super.getView(position, convertView, parent);

            ((TextView) v).setTextSize(16);
            ((TextView) v).setTypeface(type);

            Log.v("estoy aqui", items.toString());

            return v;

        }

        public View getDropDownView(int position, View convertView,ViewGroup parent) {

            View v = super.getDropDownView(position, convertView,parent);

            ((TextView) v).setGravity(Gravity.CENTER);
            ((TextView) v).setTypeface(type);

            return v;

        }

    };

    dropdown.setAdapter(adapter);


    etNombre.setTypeface(type);
    etPassword.setTypeface(type);
    etCorreo.setTypeface(type);
    etRespuesta.setTypeface(type);
    btnCrearCuenta.setTypeface(type);
    informacion.setTypeface(type);

    btnCrearCuenta.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            if ( etNombre.getText().toString().equals("") || etPassword.getText().toString().equals("") || etCorreo.getText().toString().equals("") || etRespuesta.toString().equals("")) {
                if (etNombre.getText().toString().equals("")) {
                    Toast ToastVacio = Toast.makeText(getApplicationContext(), "No has puesto el nombre", Toast.LENGTH_LONG);
                    ToastVacio.show();
                }

                else if (etPassword.getText().toString().equals("")) {
                    Toast ToastVacio = Toast.makeText(getApplicationContext(), "No has puesto la contraseña", Toast.LENGTH_LONG);
                    ToastVacio.show();
                }

                else if (etCorreo.getText().toString().equals("")) {
                    Toast ToastVacio = Toast.makeText(getApplicationContext(), "No has puesto el correo", Toast.LENGTH_LONG);
                    ToastVacio.show();
                }

                else if (etRespuesta.getText().toString().equals("")) {
                    Toast ToastVacio = Toast.makeText(getApplicationContext(), "No has puesto una respuesta", Toast.LENGTH_LONG);
                    ToastVacio.show();
                }
            }

            else {
                nombre = etNombre.getText().toString();
                password = etPassword.getText().toString();
                correo = etCorreo.getText().toString();
                eleccion = dropdown.getSelectedItem().toString();
                respuesta = etRespuesta.getText().toString();

                if (informacion.isChecked()) {
                    info = 1;
                }

                else {
                    info = 0;
                }

                new CrearNuevoUsuario().execute();


            }

        }
    });

}


@SuppressLint("StaticFieldLeak")
class CrearNuevoUsuario extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(CrearCuenta.this);
        pDialog.setMessage("Creando Usuario");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();

    }

    /**
     * Creating product
     * */
    protected String doInBackground(String... args) {
        // Building Parameters


        infostring = Integer.toString(info);


        List<NameValuePair> params = new ArrayList<>();
        params.add(new BasicNameValuePair ("nombre", nombre));
        params.add(new BasicNameValuePair("clave", password));
        params.add(new BasicNameValuePair("correo", correo));
        params.add(new BasicNameValuePair("pregunta", eleccion));
        params.add(new BasicNameValuePair("respuesta", respuesta));
        params.add(new BasicNameValuePair("informacion", infostring));

        Log.v("nombre", nombre);
        Log.v("clave", password);
        Log.v("correo", correo);
        Log.v("eleccion", eleccion);
        Log.v("respuesta", respuesta);
        Log.v("informacion", infostring);

        // getting JSON Object
        // Note that create product url accepts POST method
        JSONObject json = jsonParser.makeHttpRequest(url_crear_usuario,
                "POST", params);

        Log.v("params", params.toString());


        // check log cat fro response
        Log.d("Create Response", json.toString());

        // check for success tag
        try {
            int success = json.getInt(TAG_SUCCESS);

            if (success == 1) {
                // successfully created product
                Intent i = new Intent(getApplicationContext(), InicioPersonaje.class);
                startActivity(i);

                // closing this screen
                finish();
            } else {
                // failed to create product
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }


        return null;
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once done
        pDialog.dismiss();
    }

}
}

Greetings to all, and I hope you can help me, I am very well android studio and I am a programmer, but I do not have much idea of servers and php and I am starting in that field.

Thanks in advance.

JSONparser.java class:

package com.example.bruno.thulin.json;

import android.util.Log;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;

public class JSONparser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONparser() {

}

// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,
                                  List<NameValuePair> params) {

    // Making HTTP request
    try {

        // check for request method
        if(method == "POST"){
            // request method is POST
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        }else if(method == "GET"){
            // request method is GET
            DefaultHttpClient httpClient = new DefaultHttpClient();
            String paramString = URLEncodedUtils.format(params, "utf-8");
            url += "?" + paramString;
            HttpGet httpGet = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();
        }

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;

}
}