function _block_get_cache_id

Assemble the cache_id to use for a given block.

The cache_id string reflects the viewing context for the current block instance, obtained by concatenating the relevant context information (user, page, ...) according to the block's cache settings (BLOCK_CACHE_* constants). Two block instances can use the same cached content when they share the same cache_id.

Theme and language contexts are automatically differenciated.

Parameters

$block:

Return value

The string used as cache_id for the block.

File

modules/block/block.module, line 570

Controls the boxes that are displayed around the main content.

Code

function _block_get_cache_id($block) {
  global $theme, $base_root, $user;

  // User 1 being out of the regular 'roles define permissions' schema,
  // it brings too many chances of having unwanted output get in the cache
  // and later be served to other users. We therefore exclude user 1 from
  // block caching.
  if (variable_get('block_cache', 0) && $block->cache != BLOCK_NO_CACHE && $user->uid != 1) {
    $cid_parts = array();

    // Start with common sub-patterns: block identification, theme, language.
    $cid_parts[] = $block->module;
    $cid_parts[] = $block->delta;
    $cid_parts[] = $theme;
    if (module_exists('locale')) {
      global $language;
      $cid_parts[] = $language->language;
    }

    // 'PER_ROLE' and 'PER_USER' are mutually exclusive. 'PER_USER' can be a
    // resource drag for sites with many users, so when a module is being
    // equivocal, we favor the less expensive 'PER_ROLE' pattern.
    if ($block->cache & BLOCK_CACHE_PER_ROLE) {
      $cid_parts[] = 'r.' . implode(',', array_keys($user->roles));
    }
    elseif ($block->cache & BLOCK_CACHE_PER_USER) {
      $cid_parts[] = "u.{$user->uid}";
    }
    if ($block->cache & BLOCK_CACHE_PER_PAGE) {
      $cid_parts[] = $base_root . request_uri();
    }
    return implode(':', $cid_parts);
  }
}