PDO连接错误

Question

I am trying to connect a DB created on XAMPP. This is my code:

$dbh = new PDO("mysql:host=127.0.0.1:3306;dbname=board","root","",array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));

And the error I am getting is :

Error!: could not find driver

I am new to PHP. Has anyone else faced similar problems?