public function validate_form()
    {
        $data = array('success' => false, 'messages' => array());
        $this->form_validation->set_rules('username', 'Username', 'required|trim|xss_clean|callback_username_check');
        $this->form_validation->set_rules('password', 'Password', 'required|trim|xss_clean|callback_password_check');
        $this->form_validation->set_error_delimiters('<p class="text-danger">', '</p>');
        if ($this->form_validation->run()) {
            $data['success'] = true;
            $this->session->set_userdata('admin_username', $this->input->post('username'));
        } else {
            foreach ($_POST as $key => $value) {
                $data['messages'][$key] = form_error($key);
            }
        }

        echo json_encode($data);
    }

    public function username_check()
    {
        $username = $this->input->post("username");
        if ($this->admin_model->usernameDB()) {
            return true;
        } else {
            $this->form_validation->set_message('username_check', 'The {field} is not correct');
            return false;
        }
    }

    public function password_check()
    {
        $password = $this->input->post("password");
        if ($this->admin_model->passwordDB($password)) {
            return true;
        } else {
            $this->form_validation->set_message('password_check', 'The {field} is not correct');
            return false;
        }
    }

public function usernameDB() {
        $this->db->where('username', $this->input->post('username'));
        $query = $this->db->get('adminuser');

        if ($query->num_rows() == 1) {
            return true;
        } else {
            return false;
        }
    }

    public function passwordDB() {
        $this->db->where('password', md5($this->input->post('password')));
        $query = $this->db->get('adminuser');

        if ($query->num_rows() == 1) {
            return true;
        } else {
            return false;
        }
    }

$("#admin_login_form").submit(function(e) {
        e.preventDefault();
        var me = $(this);
        // perform ajax
        $.ajax ({
            url: "validate_form",
            type: "post",
            data: me.serialize(),
            dataType: "json",
            success: function(response) {
                if (response.success == true) {
                    $('.form-group').removeClass('has-error')
                                    .removeClass('has-success');
                    $('.text-danger').remove();
                    window.location = "member";
                } else {
                    $.each(response.messages, function(key, value) {
                        var element = $('#' + key);
                        element.closest('div.form-group')
                        .removeClass('has-error')
                        .addClass(value.length > 0 ? 'has-error' : 'has-success')
                        .find('.text-danger')
                        .remove();
                        element.after(value);
                    });
                }
            }
        });
    });