<?php
    if($this->input->post('submit'))
    {
        $username = $this->input->post('username');
        $password = $this->input->post('password');

        $this->db->select('username,password,admin_id');
        $this->db->from('admin');
        $where = "username='$username' and password = '$password'";
        $this->db->where($where);
        $query = $this->db->get();
        $result = $query->row_array();
        $num = $query->num_rows();
        if($num > 0)
        {
            $this->session->set_userdata('admin_id',$result);
            redirect('admin/home');
        }
        else
        {
            echo "<p style='color: red;font-weight: 400;margin-right: 60px;'>Wrong email id or password! </p>";
        }
    }
?>
<form class="form-signin" method="post">
    <input type="text" name="username" id="username" class="form-control" placeholder="username" required autofocus>
    <input type="password" name="password" id="password" class="form-control" placeholder="Password" required>
    <input type="submit" id="submit" name="submit" class="btn btn-lg btn-primary btn-block" value="Sign In">
</form>

<?php
defined('BASEPATH') OR exit('No direct script access allowed');
class Admin extends CI_Controller {
    function __construct()
    {
        parent :: __construct();
        $this->load->helper(array('form', 'url', 'captcha', 'email'));
        $this->load->model('ad_data');
    }
    public function home()
    {
        $data['admin_id'] = $this->session->userdata('admin_id');
        print_r($data['admin_id']);
    }
}