public function closeAll()
{
$this->closeWriteConnection();
if ($this->total_read_count >= 1 && is_array(self::$read_conn_pool)) {
foreach (self::$read_conn_pool as $key => $db) {
if (!is_null($db)) {
$db->close();
self::$read_conn_pool[$key] = null;
}
}
self::$read_conn_pool = null;
}
}