From Joomla! Documentation
The "API15" namespace is an archived namespace. This page contains information for a Joomla! version which is no longer supported. It exists only as a historical reference, it will not be improved and its content may be incomplete and/or contain broken links.
JCacheCallback is a concrete cache handler. It caches and returns the output and results of callback functions.
|call||Executes a cacheable callback if not found in cache else returns cached output and result|
|get||Executes a cacheable callback if not found in cache else returns cached output and result|
jimport( 'joomla.cache.handler.callback' );