The block or element can change depending on the user.
This setting can be resource-consuming for sites with large number of users, and thus should only be used when DRUPAL_CACHE_PER_ROLE is not sufficient.
File
- includes/
common.inc, line 146 - Common functions that many Drupal modules will need to reference.
Code
define('DRUPAL_CACHE_PER_USER', 0x0002)