Help finding a bug in a loop that doesn't pass the result of a variable to an XML feed?

Question

PHP

I am writing an xml feed. This code is responsible for displaying the image. But for some reason it outputs nothing. Please help to display the url of the photo.

Looping an image to find a link to a photo

$images = '';

          foreach ($this->model_catalog_product->getProductImages($product['product_id']) as $image)

          {	if ($image['image']) {

              $link = $this->model_tool_image->resize($image['image'], $this->config->get($this->config->get('config_theme') . '_image_popup_width'), $this->config->get($this->config->get('config_theme') . '_image_popup_height'));

              $images .= '<image>' . $link . '</image>';

            }

          }

What forms the markup of the feed
$output .= '<images>'. $images . '</images>';