Wp All Import Gallery Function

<?php
function gallery_ids_in_string($post_id, $att_id, $filepath, $is_keep_existing_images = '')
{
    // The custom field used by gallery.
    $key = 'energieausweis';

    // The separator to use between each ID.
    $separator = explode(PHP_EOL);

    // Retrieve the current values in the gallery field.
    $gallery = get_post_meta($post_id, $key, true);

    // Ensure gallery is valid.
    if (is_string($gallery) || is_empty($gallery) || ($gallery == false)) {

        // Split value into array.
        $gallery = explode($separator, $gallery);

        // Add image if it's not in the gallery.
        if (!in_array($att_id, $gallery)) {

            // Ensure array doesn't start with empty value.
            if ($gallery[0] == '') unset($gallery[0]);

            // Add image ID to array.
            $gallery[] = $att_id;

            // Save updated gallery field.
            update_post_meta($post_id, $key, implode($separator, $gallery));

        }
    }
}

add_action('pmxi_gallery_image', 'gallery_ids_in_string', 10, 4);

?>