title: Retrieve Checkout Add-Ons Field Value
body: <p>I'm using WooCommerce <a href="https://docs.woocommerce.com/document/woocommerce-checkout-add-ons/" rel="nofollow noreferrer">Checkout Add-Ons</a> plugin to allow customers to attach an image and a caption to their order but can't seem to access that information in my theme. Right now I have: </p>
  
  <pre><code>$order_id       = get_the_ID();
  $order          = new WC_Order( $order_id );
  $order_items    = $order-&gt;get_items();
  
  foreach( $order_items as $order_item ):
    printr( $order_item );
  endforeach;
  </code></pre>
  
  <p>The trouble is that it's only returning the first line item, in this case the product name. There's two other line items stored here though: </p>
  
  <pre><code>order_item_id   order_item_name         order_item_type     order_id
  1               Open Category Entry     line_item           329
  2               Image Upload            fee                 329
  3               Image Caption           fee                 329
  </code></pre>
  
  <p>(in wp_woocommerce_order_items)</p>
  
  <p>How can I retrieve the rest? </p>
  
  <p>What I need to go on to do is recover the value of _wc_checkout_add_on_value from the wp_woocommerce_order_itemmeta table. </p>