/**
* Flushes all data
*
* @param string $group Used to differentiate between groups of cache values
* @return boolean
*/
function flush($group = '')
{
@set_time_limit($this->_flush_timelimit);
$flush_dir = $group ? $this->_cache_dir . DIRECTORY_SEPARATOR . $group . DIRECTORY_SEPARATOR : $this->_flush_dir;
Util_File::emptydir($flush_dir, $this->_exclude);
return true;
}