On 'product list page' I need an extra icon to appear when the product has an url.

On the 'product list page' I need an extra icon to appear over a products image when the product has a "product url".

I thought it would be something like:

Any ideas?
Regards,
Carlos.

$products_url is not used in product_listing.php. I don't have time at the moment to see if it is available from upstream - have you checked this? If it is available, your code looks good. If not, you would have to add that to the list of fields retrieved from the db upstream and put it into the appropriate array.

Sorry, I'm not that experienced, is there anybody that knows how to do it?

Do you know where I can find the specific list of field?

you need to add (pd.products_url) to your /includes/index_filters/YOUR_TEMPLATE/default_filter.php file in 4 different places

look for something that starts like this:
// We are asked to show only a specific category
$listing_sql = "select " . $select_column_list . " p.products_id,

ADD:
pd.products_url,

you will need to do this in 4 places in that file

then in /includes/modules/YOUR_TEMPLATE/product_listing.php

Find:
$lc_text = '<a href="' . zen_href_link(zen_get_info_page($listing->fields['products_id']), 'cPath=' . (($_GET['manufacturers_id'] > 0 and $_GET['filter_id']) > 0 ? zen_get_generated_category_path_rev($_GET['filter_id']) : ($_GET['cPath'] > 0 ? zen_get_generated_category_path_rev($_GET['cPath']) : zen_get_generated_category_path_rev($listing->fields['master_categories_id']))) . '&products_id=' . $listing->fields['products_id']) . '">' . zen_image(DIR_WS_IMAGES . $listing->fields['products_image'], $listing->fields['products_name'], IMAGE_PRODUCT_LISTING_WIDTH, IMAGE_PRODUCT_LISTING_HEIGHT, 'class="listingProductImage"') . '</a>';

ADD after it:

if (zen_not_null($listing->fields['products_url'])) {
$lc_text .= zen_image(DIR_WS_IMAGES . 'dm.gif', 'ADD_IMAGE_ALT_HERE', 'ADD_IMAGE_WIDTH_HERE','ADD_IMAGE_HEIGHT_HERE', 'class="imageOverlay"');
}

but before:
}
}
break;

Dear rbarbour,

Thank you so much for helping me out!!

np, glad I could help!