Change password in CodeIgniter with callback validation for check old password.

Controller

application/controllers/Users.php

defined('BASEPATH') OR exit('No direct script access allowed');

class Users extends CI_Controller{
    
    public function __construct()
    {
        parent::__construct();
        $this->load->helper('form');
        $this->load->library('form_validation');
        $this->load->model('users_model');
    }
    
    private function logged_in()
    {
        if( ! $this->session->userdata('authenticated')){
            redirect('users/login');
        }
    }
    
    public function changePassword()
    {
        $this->logged_in();

        $data['title'] = 'Change Password';

        $this->load->library('form_validation');

        $this->form_validation->set_rules('oldpass', 'old password', 'callback_password_check');
        $this->form_validation->set_rules('newpass', 'new password', 'required');
        $this->form_validation->set_rules('passconf', 'confirm password', 'required|matches[newpass]');

        $this->form_validation->set_error_delimiters('
', '
');

        if($this->form_validation->run() == false) {
            $this->load->view('header', $data);
            $this->load->view('users/change_password', $data);
            $this->load->view('footer', $data);
        }
        else {

            $id = $this->session->userdata('id');

            $newpass = $this->input->post('newpass');

            $this->users_model->update_user($id, array('password' => md5($newpass)));

            redirect('users/logout');
        }
    }

    public function password_check($oldpass)
    {
        $id = $this->session->userdata('id');
        $user = $this->users_model->get_user($id);

        if($user->password !== md5($oldpass)) {
            $this->form_validation->set_message('password_check', 'The {field} does not match');
            return false;
        }

        return true;
    }
}
?>

Model

application/models/Users_model.php

defined('BASEPATH') OR exit('No direct script access allowed');

class Users_model extends CI_Model{
    
    public function get_user($id)
    {
        $this->db->where('id', $id);
        $query = $this->db->get('users');
        return $query->row();
    }

    public function update_user($id, $userdata)
    {
        $this->db->where('id', $id);
        $this->db->update('users', $userdata);
    }
}
?>

div class="row justify-content-center">
    <div class="col-6">
        <h1> echo $title ?>h1>
         echo form_open('users/changePassword', array('id' => 'passwordForm'))?>
            <div class="form-group">
                <input type="password" name="oldpass" id="oldpass" class="form-control" placeholder="Old Password" />
                 echo form_error('oldpass', '
', '
')?>
            div>
            <div class="form-group">
                <input type="password" name="newpass" id="newpass" class="form-control" placeholder="New Password" />
                 echo form_error('newpass', '
', '
')?>
            div>
            <div class="form-group">
                <input type="password" name="passconf" id="passconf" class="form-control" placeholder="Confirm Password" />
                 echo form_error('passconf', '
', '
')?>
            div>
            <div class="form-group">
                <button type="submit" class="btn btn-success">Change Passwordbutton>
            div>
         echo form_close(); ?>
    div>
div>