7.x theme.inc drupal_find_base_themes($themes, $key, $used_keys = array())

Find all the base themes for the specified theme.

Themes can inherit templates and function implementations from earlier themes.


$themes: An array of available themes.

$key: The name of the theme whose base we are looking for.

$used_keys: A recursion parameter preventing endless loops.

Return value

Returns an array of all of the theme's ancestors; the first element's value will be NULL if an error occurred.

2 calls to drupal_find_base_themes()
system_find_base_themes in modules/system/system.module
Find all the base themes for the specified theme.
_system_rebuild_theme_data in modules/system/system.module
Helper function to scan and collect theme .info data and their engines.


includes/theme.inc, line 843
The theme system, which controls the output of Drupal.


function drupal_find_base_themes($themes, $key, $used_keys = array()) {
  $base_key = $themes[$key]->info['base theme'];

  // Does the base theme exist?
  if (!isset($themes[$base_key])) {
    return array(
      $base_key => NULL,
  $current_base_theme = array(
    $base_key => $themes[$base_key]->info['name'],

  // Is the base theme itself a child of another theme?
  if (isset($themes[$base_key]->info['base theme'])) {

    // Do we already know the base themes of this theme?
    if (isset($themes[$base_key]->base_themes)) {
      return $themes[$base_key]->base_themes + $current_base_theme;

    // Prevent loops.
    if (!empty($used_keys[$base_key])) {
      return array(
        $base_key => NULL,
    $used_keys[$base_key] = TRUE;
    return drupal_find_base_themes($themes, $base_key, $used_keys) + $current_base_theme;

  // If we get here, then this is our parent theme.
  return $current_base_theme;