Android index php file does not register the user

Hey guys im currently following this tutorial by android hive on how to create a Login and Registration system using PHP and MYSQL however im having some difficulties with registering a user. I really appreciate your time for reading this post, thank you.

android hive tutorial link: http://ift.tt/1gfNOBZ

image of LogCat when the "Register" button is clicked: http://ift.tt/1MGIJBv

I have tried using the Advanced Rest Client extension for Google Chrome however it didnt really provide me with any useful information.

index.php file which contains all the functions for storing and getting the data of the users from the database:

<?php
//this file has the role fo accepting requests and giving JSON responses.
// Accepts POST and GET requests


if (isset($_POST['tag']) && $_POST['tag'] != ''){
    //get the tag
    $tag = $_POST['tag'];

    //include a database handler
    require_once 'login_api/DB_Functions.php';
    $db = new DB_Functions();

    //reponse array
    $response = array("tag" => $tag, "error" => FALSE);

    //check for the tag type
    if ($tag == 'login'){
        //request type is going to be to check the login
        $email = $_POST['email'];
        $password = $_POST['password'];

        //check for the user
        $user = $db->getUsersByEmailAndPassword($email, $password);
        if ($user != false){
            //this mean the user has been found
            $response["error"] = FALSE;
            $response["uid"] = $user["unique_id"];
            $response["user"]["name"] = $user["name"];
            $response["user"]["email"] = $user["email"];
            $response["user"]["created"] = $user["created"];
            $response["user"]["updated"] = $user["updated"];
            echo json_encode($response);
        }else {
            //user is not found
            //echo the json with error = 1
            $response["error"] = TRUE;
            $response["error_msg"] = "Incorrect email or password";
            echo json_response($response);
        }
    }else if ($tag == 'register') {
        //request type is to register a new user
        $name = $_POST['name'];
        $email = $_POST['email'];
        $password = $_POST['password'];

        //check to see if the user already exists
        if ($db->isUserExisted($email)){
            //user already exists so produce an error response
            $response["error"] = TRUE;
            $response["error_msg"] = "User Already Exists";
            echo json_encode($response);
        }else{
            //store user
            $user = $db->storeUser($name, $email, $password);
            if ($user){
                //user is stored successfully
                //Creating the data for JSON
                $response["error"] = FALSE;
                $response["uid"] = $user["unique_id"];
                $response["user"]["name"] = $user["name"];
                $response["user"]["email"] = $user["email"];
                $response["user"]["created"] = $user["created"];
                $response["user"]["updated"] = $user["updated"];
                echo json_encode($response);
            }else{
                //failure storing the user details into the database
                $response["error"] = TRUE;
                $response["error_msg"] = "An error has occured with registering..";
                echo json_encode($response);
            }
        }
        }else {
        //user failed to store
        $response["error"] = TRUE;
        $response["error_msg"] = "Uknown 'tag', should be either login or  register";
        echo json_encode($response);
        }
    }else {
    $response["error"] = TRUE;
    $response["error_msg"] = "Required, 'tag' is missing";
    echo json_encode($response);
    }

?>

my RegisterActivity:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_register);

    inputFullName = (EditText) findViewById(R.id.name);
    inputEmail = (EditText) findViewById(R.id.email);
    inputPassword = (EditText) findViewById(R.id.password);
    btnRegister = (Button) findViewById(R.id.btnRegister);
    btnLinkToLogin = (Button) findViewById(R.id.btnLinkToLoginScreen);

    // Progress dialog
    pDialog = new ProgressDialog(this);
    pDialog.setCancelable(false);

    // Session manager
    session = new SessionManager(getApplicationContext());

    // SQLite database handler
    db = new SQLiteHandler(getApplicationContext());

    // Check if user is already logged in or not
    if (session.isLoggedIn()) {
        // User is already logged in. Take him to main activity
        Intent intent = new Intent(RegisterActivity.this,
                MainActivity.class);
        startActivity(intent);
        finish();
    }

    // Register Button Click event
    btnRegister.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            String name = inputFullName.getText().toString();
            String email = inputEmail.getText().toString();
            String password = inputPassword.getText().toString();

            if (!name.isEmpty() && !email.isEmpty() && !password.isEmpty()) {
                registerUser(name, email, password);
            } else {
                Toast.makeText(getApplicationContext(),
                        "Please enter your details!", Toast.LENGTH_LONG)
                        .show();
            }
        }
    });

    // Link to Login Screen
    btnLinkToLogin.setOnClickListener(new View.OnClickListener() {

        public void onClick(View view) {
            Intent i = new Intent(getApplicationContext(),
                    LoginActivity.class);
            startActivity(i);
            finish();
        }
    });

}

/**
 * Function to store user in MySQL database will post params(tag, name,
 */
private void registerUser(final String name, final String email,
                          final String password) {
    // Tag used to cancel the request
    String tag_string_req = "req_register";

    pDialog.setMessage("Registering ...");
    showDialog();

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

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

            try {
                JSONObject jObj = new JSONObject(response);
                boolean error = jObj.getBoolean("error");
                if (!error) {
                    // User successfully stored in MySQL
                    // Now store the user in sqlite
                    String uid = jObj.getString("uid");

                    JSONObject user = jObj.getJSONObject("user");
                    String name = user.getString("name");
                    String email = user.getString("email");
                    String created = user
                            .getString("created");

                    // Inserting row in users table
                    db.addUser(name, email, uid, created);

                    // Launch login activity
                    Intent intent = new Intent(
                            RegisterActivity.this,
                            LoginActivity.class);
                    startActivity(intent);
                    finish();
                } else {

                    // Error occurred in registration. Get the error
                    // message
                    String errorMsg = jObj.getString("error_msg");
                    Toast.makeText(getApplicationContext(),
                            errorMsg, Toast.LENGTH_LONG).show();
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    }, new Response.ErrorListener() {

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

        @Override
        protected Map<String, String> getParams() {
            // Posting params to register url
            Map<String, String> params = new HashMap<String, String>();
            params.put("tag", "register");
            params.put("name", name);
            params.put("email", email);
            params.put("password", password);

            return params;
        }

    };

    // Adding request to request queue
    AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}

private void showDialog() {
    if (!pDialog.isShowing())
        pDialog.show();
}

private void hideDialog() {
    if (pDialog.isShowing())
        pDialog.dismiss();
}
}