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//pobieranie featured image
function ST4_get_featured_image($post_ID) {
    $post_thumbnail_id = get_post_thumbnail_id($post_ID);
    if ($post_thumbnail_id) {
        $post_thumbnail_img = wp_get_attachment_image_src($post_thumbnail_id, 'featured_preview');
        return $post_thumbnail_img[0];
    }
}

// Add to admin_init function
add_filter('manage_edit-produkty_columns', 'add_new_produkty_columns');

function add_new_produkty_columns($gallery_columns) {
    $new_gc =$gallery_columns;
    
    unset($new_gc["date"]);
    
    $new_gc['kod']=__('ID');
    $new_gc['images']=__('Zdjęcie');
    
    return $new_gc;
}

// Add to admin_init function
add_action('manage_produkty_posts_custom_column', 'manage_produkty_columns', 10, 2);

function manage_produkty_columns($column_name, $id) {
    global $wpdb;
    switch ($column_name) {
        case 'kod':
            echo get_field('kod',$id);
            break;

        case 'images':
            // Get number of images in gallery
            $post_featured_image = ST4_get_featured_image($id);
            if ($post_featured_image) {
                // HAS A FEATURED IMAGE
                echo '<img src="' . $post_featured_image . '" />';
            }
            break;
        default:
            break;
    } // end switch
}