I use the following statement to clear the cache:

$cache->clean(Zend_Cache::CLEANING_MODE_MATCHING_TAG,array($uid,'PERMISSIONS'));

There is no way to clear the cache at this time, I made sure the tags consisting of $uid and PERMISSIONS are correct. My cache save code is:

$cache_tag=array($uid,'PERMISSIONS'); $cache->save($cache_data,$cache_id,$cache_tag);

When I use the following method, it can be cleared

$cache->clean(Zend_Cache::CLEANING_MODE_ALL);

Why is this? ?