ต้องแก้ไขอย่างไรครับ

Fatal error: Uncaught exception 'PDOException' with message 'could not find driver' in C:\xampp\htdocs\phptest\index.php:8 Stack trace: #0 C:\xampp\htdocs\phptest\index.php(8): PDO->__construct('mysql : host=lo...', 'root', '', Array) #1 {main} thrown in C:\xampp\htdocs\phptest\index.php on line 8


1      <?php
2      $dsn = 'mysql : host=localhost';
3      $username = 'root';
4      $password = 'root';
5      $option  = array(
6      PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES uft8',
7      ) ;
8      $dbh = new PDO($dsn, $username, $password, $option);
9      echo 'ติดต่อ ฐานข้อมูลสำเร้จ';
10    
11    ?>