In drupal 7 check if page is using panels is just one line of code but comes in handy very often. Some times you need to do some decisions in the page template based on it.

Many times I come across a situation where a page should display breadcrumbs or not based on whether the page is being handled by a panel layout or not.

A simple call for the the panels_get_current_page_display will do the trick. Just place the following code in your themes template.php file.

 * Implements hook_preprocess_page().
function YOURTEHME_preprocess_page(&$variables) {
  $variables['using_panels'] = false;
  $panel = panels_get_current_page_display();
  if ( isset($panel) && !empty($panel->layout) ) {
      $variables['using_panels'] = true;

$using_panels is now available in your page template.