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Definition

cache_set($cid, $data, $table = 'cache', $expire = CACHE_PERMANENT, $headers = NULL)
drupal/includes/cache.inc, line 106

Description

Store data in the persistent cache.

The persistent cache is split up into four database tables. Contributed modules can add additional tables.

'cache_page': This table stores generated pages for anonymous users. This is the only table affected by the page cache setting on the administrator panel.

'cache_menu': Stores the cachable part of the users' menus.

'cache_filter': Stores filtered pieces of content. This table is periodically cleared of stale entries by cron.

'cache': Generic cache storage table.

The reasons for having several tables are as follows:

  • smaller tables allow for faster selects and inserts
  • we try to put fast changing cache items and rather static ones into different tables. The effect is that only the fast changing tables will need a lot of writes to disk. The more static tables will also be better cachable with MySQL's query cache

Parameters

$cid The cache ID of the data to store.

$data The data to store in the cache. Complex data types will be automatically serialized before insertion. Strings will be stored as plain text and not serialized.

$table The table $table to store the data in. Valid core values are 'cache_filter', 'cache_menu', 'cache_page', or 'cache'.

$expire One of the following values:

  • CACHE_PERMANENT: Indicates that the item should never be removed unless explicitly told to using cache_clear_all() with a cache ID.
  • CACHE_TEMPORARY: Indicates that the item should be removed at the next general cache wipe.
  • A Unix timestamp: Indicates that the item should be kept at least until the given time, after which it behaves like CACHE_TEMPORARY.
$headers A string containing HTTP header information for cached pages.

Code

function cache_set($cid, $data, $table = 'cache', $expire = CACHE_PERMANENT, $headers = NULL) {
  $fields = array(
    'serialized' => 0,
    'created' => REQUEST_TIME,
    'expire' => $expire,
    'headers' => $headers,
  );
  if (!is_string($data)) {
    $fields['data'] = serialize($data);
    $fields['serialized'] = 1;
  }
  else {
    $fields['data'] = $data;
    $fields['serialized'] = 0;
  }

  db_merge($table)
    ->key(array('cid' => $cid))
    ->fields($fields)
    ->execute();
}