Determine if current page is a panel (Drupal themes)
Snippet that adds "panels" to the body classes of a page if the currently-viewed page is a panel:
function zen_preprocess_page(&$vars, $hook) {
$vars['body_classes_array'][] = (module_exists('page_manager') && (page_manager_get_current_page())) ? 'panels' : ''; // Page is Panels page
// $vars['sample_variable'] = t('Lorem ipsum.');
}