Codeigniter ignoring a function? - php

Question

I'm new to CodeIgniter and have only started learning ajax. I'm trying to make a web-based management system using codeigniter, a distant relative gave me a sample of his system using codeigniter for reference before he left to work abroad. but I'm having problem with the login page of his system it keeps on refreshing the login page.
here is the login page.
<?php
defined('BASEPATH') OR exit('No direct script access allowed');
class Login extends CM_Controller {
public function __construct()
{
parent::__construct();
}
public function index()
{
$this->generate_login_page('backbone/login', [
'title'=>'CCC case management system - Login',
'js'=>['modules/home/login.js']
]);
}
public function authenticate_login() {
//$this->output->set_content_type('json');
//$this->form_validation->set_rules('username', '<strong>Username</strong>', 'required');
//$this->form_validation->set_rules('password', '<strong>Password</strong>', 'required');
//if($this->form_validation->run()){
$input = elements(['username','password'], $this->input->post());
$input['username'] = ucwords($input['username']);
$input['password'] = sha1($input['password']);
$result = $this->login_model->check_user_exist($input['username']);
//echo $input['username'];
//echo $result;
if($input['username'] !== ''){
if($result)
{
$result_match = $this->login_model->check_user_password_match($input['username'],$input['password'] );
//echo ''.;
if($result_match)
{
$result_user = $this->login_model->retrieve_user_information($input['username']);
$user_type_id = 0;
$user_id = 0;
if($result_user->num_rows() > 0){
foreach ($result_user->result() as $row) {
$user_type_id = $row->user_type_id;
$user_id = $row->user_id;
$username = $row->username;
}
}
//echo json_encode($result_user);
$session_data = array(
'username' => $username,
'session_id' => $this->session->userdata('session_id'),
'user_id' => $user_id,
'user_type_id' =>$user_type_id,
'is_logged_in' => 1
);
$this->session->set_userdata($session_data);
$this->session->set_userdata('login_state', TRUE);
redirect('/');
}
else
{
$this->session->set_flashdata('msg', 'Incorrect Password or Username!');
redirect('login/');
//
//echo 'Username or Password is incorrect';
//$this->output->set_output($this->set_json_output(FALSE, 'Username or Password is incorrect'));
}
}
else
{
$this->session->set_flashdata('msg', 'Invalid Username or doesnt exist !');
redirect('login/');
//
//$this->output->set_output($this->set_json_output(FALSE, 'User not Exist'));
//echo 'User not registered';
}
}else{
$this->session->set_flashdata('msg', 'Please input username !');
redirect('login/');
}
/*}else{
$error_messages = array_values($this->form_validation->error_array());
$this->output->set_output($this->set_json_output(FALSE, $error_messages));
}*/
}
}
if username and password match from database is should redirect to another page. if not a message should pop out for incorrect user / pass.
im not getting any errors but the problem is it does not redirect to another page it only keeps on refreshing the page and also if i leave user and pass empty / give an incorrect user & pass input the same thing happens. it seems like the function authenticate_login is not being executed? can anyone tell me what exactly is wrong here. Tnx.