login session

<?php
defined('BASEPATH') OR exit ('No direct access allowed');

class Login extends CI_Controller {
    public function __construct()
    {
        parent::__construct();
        $this->load->library('session');
        $this->load->model('kuale');




    }
    public function ceklogin()
    {

        if(isset($_POST['login'])){
        $username = $this->input->post('username',true);
        $password = $this->input->post('password',true);
        $cek = $this->kuale->proseslogin($username,$password);
        $hasil = count($cek);
        echo $hasil;
        if($hasil > 0){
            $pelogin = $this->db->get_where('user',array('username' => $username, 'password' => $password))->row();
            $this->session->set_userdata($data);
            if($pelogin->level == 'admin'){
                redirect('admin/index');
            }elseif($pelogin->level == 'pelayan'){
                redirect('admin/pesan');
            }elseif($pelogin->level == 'kasir'){
                redirect('admin/kasir');
            }
        }

        else{
            echo"<script> alert('Username atau Password anda salah');
                window.history.back();</script>";

            }

        }
    }
}