Simple User Login Class CodeIgniter

user.php

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

/*
 * statuses:
 * 0 - banned
 * 1 - member
 * 2 - moderator
 * 3 - admin
 *
 *
 * */

class User {

    public $error;

    public $data = array();

    public function User()
    {
        $this->CI =& get_instance();
        log_message('debug', 'User class initialized');
    }

    public function create_table()
    {
        $sql = "create table if not exists users(
        id smallint unsigned not null auto_increment primary key,
        username varchar(255) not null,
        password varchar(255) not null,
        email varchar(255) not null,
        ip varchar(15) not null,
        status tinyint not null default 1
        );";
        $this->CI->db->query($sql);

        return 'Done';

    }

    public function drop_table()
    {
        $sql = 'drop table users;';
        $this->CI->db->query($sql);
        return 'Done';
    }

    /*
     * @input array('username' => 'admin', 'password' => 'pass', 'email' => 'mail@gmail.com', 'ip' => '127.0.0.1', 'status' => 1)
     * @inpput true or false for check email and ip default true
     * */

    public function register( $data, $emailcheck=true, $ipcheck=true)
    {
        if( empty($data['username']) || empty($data['email']) || empty($data['password']) ) {
            return $this->error = 'Data is emptty';
        }
        if($ipcheck) {
            if( $this->CI->db->get_where('users', array('ip' => $_SERVER['REMOTE_ADDR']))->num_rows() > 0 ) {
                $this->error = "IP {$_SERVER['REMOTE_ADDR']} already assigned to an account.";
                return $this->error;
            }
        }

        if($emailcheck) {
            if( $this->CI->db->get_where('users', array('email' => $data['email']))->num_rows > 0 ) {
                $this->error = "This {$data['email']} already taken.";
                return $this->error;
            }
        }

        if( $this->CI->db->get_where('users', array('username' => $data['username']))->num_rows() > 0 ) {
            $this->error = "This {$data['username']} already taken.";
            return $this->error;
        }

        $data['password'] = $this->crypt($data['password']);

        $this->CI->db->insert('users', $data);
    }

    /*
     * @input array('username' => 'username, 'password' => 'pass')
     * @ return boolean true if all good
     * @optional can return all data from row
     * */
    public function login($data, $return_all_data=false)
    {
        if( empty($data['password']) ) {
            return $this->error = 'Data password is emptty';
        }

        $data['password'] = $this->crypt( $data['password'] );

        $check = $this->CI->db->get_where('users', $data);

        if( $check->num_rows() == 0 ) {
            return false;
        }

        $Q = $check->row();
        $check->free_result();
        if($Q->status == 0) {
            //if banned
            return false;
        }

        $this->CI->session->set_userdata(array(
            'username' => $Q->username,
            'status' => $Q->status,
            'logged_in' => 1
        ));


        if($return_all_data) {
            return $Q;
        } else {
            return true;
        }

    }


    public function logged_in()
    {
        if( !empty($this->CI->session->userdata['logged_in']) AND $this->CI->session->userdata['logged_in'] === 1 ){
            return true;
        } else {
            return false;
        }
    }

    public function is_admin()
    {
        if( !empty($this->CI->session->userdata['status']) AND $this->CI->session->userdata['status'] === 3 ){
            return true;
        } else {
            return false;
        }
    }

    public function log_out()
    {
        $this->CI->session->unset_userdata('logged_in');
    }

    private function crypt($data)
    {
        return md5(md5($data));
    }

}