Adapter \Typecho\Db\Adapter\Pdo\Mysql is not available

Typecho\Db\Exception: Adapter \Typecho\Db\Adapter\Pdo\Mysql is not available in /home/W_qwqDworld/www/var/Typecho/Db.php:115 Stack trace: #0 /home/W_qwqDworld/www/config.inc.php(21): Typecho\Db->__construct() #1 /home/W_qwqDworld/www/index.php(11): include_once('...') #2 {main}