Update Line Item Meta Data – WooCommerce API

For some reason, you have to double the arrays, maybe this doesn’t affect you as you are referencing the firt element. I use this in PHP:

function saveMetaItem($id_order,$id_item,$id_product,$meta_key,$meta_value){
    $woo = new wooclient();
    $data = array(
        'line_items' => array(array(
                       'id' => $id_item,
                       'product_id' => $id_product,
                       'meta_data' => array(array(
                            'key' => $meta_key,
                            'value' => $meta_value
                               ))
                       ))
    );
    $result = $woo->put('orders/'.$id_order, $data);
    return $result;
}

Notice the double array() calls in both line_items and meta_data. Also provide both id and product_id. Convert that to JSON and your done 😉