Simple Form Post Not Working

I've been stuck here for hours and I can not seem to find the source.

I have a simple login form.

Code:

<form method="post" class="m-t" role="form" action="<?php echo base_url();?>login/">
               <div class="form-group">
                   <input type="text" name="username" id="username" class="form-control" placeholder="Username" required="">
               </div>
               <div class="form-group">
                   <input type="password" name="password" id="password"  class="form-control" placeholder="Password" required="">
               </div>
               <button type="submit" class="btn btn-primary block full-width m-b">Login</button>

               <a href="#"><small>Forgot password?</small></a>
               <p class="text-muted text-center"><small>Do not have an account?</small></p>
               <!-- <a class="btn btn-sm btn-white btn-block" href="register.html">Create an account</a>  -->
           </form>

The Controller I am Posting to looks like this:

PHP Code:

class Login extends CI_Controller {

    public function _construct()
    {
        session_start();
        parent::__construct();
    }

    public function index()
    {
        $check = $this->session->userdata('logged_in');
        if(empty($check))
        {
           $this->load->view('templates/header.php');
           $this->load->view('pages/home');
           $this->load->view('templates/header.php');
        }
        else
        {
          $st = $this->session->userdata('role');
          if($st=='worker')
          {
              header('location:'.base_url().'worker');    
          }
          else if($st=='client')
          {
              header('location:'.base_url().'client');
          }
          else if($st=='sales')
          {
              header('location:'.base_url().'sales');
          }
          else if($st=='billing')
          {
              header('location:'.base_url().'billing');
          }
        }
    }


    public function login()
    {
       print_r($_POST);
       $u = $this->input->post('username');
       $p = $this->input->post('password');
       $this->web_app_model->getLoginData($u, $p);
       
    }

} 


The POST DATA is in the array yet I get the following errors.

class Login extends CI_Controller {

    public function _construct()
    {
        session_start();
        parent::__construct();
    }

public function index()
{
$check = $this->session->userdata('logged_in');
if(empty($check))
{
   $this->load->view('templates/header.php');
       $this->load->view('pages/home');
       $this->load->view('templates/header.php');
}
else
{
  $st = $this->session->userdata('role');
  if($st=='worker')
  {
      header('location:'.base_url().'worker');    
  }
  else if($st=='client')
  {
      header('location:'.base_url().'client');
  }
  else if($st=='sales')
  {
      header('location:'.base_url().'sales');
  }
  else if($st=='billing')
  {
      header('location:'.base_url().'billing');
  }
}
}


    public function login()
    {
       print_r($_POST);
       $u = $this->input->post('username');
       $p = $this->input->post('password');
       $this->web_app_model->getLoginData($u, $p);
       
    }

}

A PHP Error was encountered
Severity: Error
Message: Call to a member function post() on null
Filename: controllers/Login.php
Line Number: 46
Backtrace:

I tried directly accessing the post data via $_POST as shown here:

PHP Code:

   public function login()
    {
       print_r($_POST);
       //$u = $this->input->post('username');
       //$p = $this->input->post('password');
       $u = $_POST['username'];
       $p = $_POST['password'];
       $this->web_app_model->getLoginData($u, $p);
       
    } 


And then I get the following errors:

A PHP Error was encountered
Severity: Notice
Message: Undefined property: Login::$web_app_model
Filename: controllers/Login.php
Line Number: 50
Backtrace:
File: C:\xampp\htdocs\mmmPortal\application\controllers\Login.php
Line: 50
Function: _error_handler
File: C:\xampp\htdocs\mmmPortal\index.php
Line: 315
Function: require_once

A PHP Error was encountered
Severity: Error
Message: Call to a member function getLoginData() on null
Filename: controllers/Login.php
Line Number: 50
Backtrace:

It seems anything that uses $this is not working yet it works in my other controllers and I've compared them over and over for basic structure errors.

Any help would be greatly appreciated!