header white Data

Hello everybody,
I wanted to include a loop in my template header.php.
Unfortunately I get with the foreach an error message.
What have I done wrong?

Controller:

PHP Code:

<?php
    class Warenkorb extends CI_Controller
        {
            function __construct()
                {
                    parent::__construct();
                }

            public function header()
                {
                    $data['header_warenkorbs'] = $this->Warenkorb_model->header_warenkorbs();
                    $this->load->view('templates/header', $data);
                    // $this->load->view('test/index');
                    // $this->load->view('templates/footer');
                }
        } 


Model:

PHP Code:

<?php
    class Warenkorb_model extends CI_Model
        {
            public function header_warenkorbs()
                {
                    $this->db->select('*');
                    $this->db->from('db_artikel');
                    $query = $this->db->get();
                    return $query->result_array();
                }
        } 


header.php

Code:

<?php foreach ($header_warenkorbs as $warenkorb): ?>
                                <li>
                                    <span class="item">
                                        <span class="item-left">
                                            <span class="item-info">
                                                <span>Item name</span>
                                                <span>23$</span>
                                            </span>
                                        </span>
                                        <span class="item-right">
                                            <button class="btn btn-xs btn-danger pull-right">x</button>
                                        </span>
                                    </span>
                                </li>
<?php endforeach; ?>