Use PDO in PIP MVC

Question

i am not new to PHP but definitely beginner in MVC stuff. I have read about MVC and get understanding that Model handles all DB operations ie. CRUD

I googled bit nd found Model.php as

class Model {

private $connection;

 public function __construct()
 {
    global $config;

    $this->connection = mysql_connect($config['db_host'], $config['db_username'], 
                        $config['db_password']) or die('MySQL Error: '. mysql_error());
    mysql_select_db($config['db_name'], $this->connection);
 }

 public function execute($qry)
 {
    $exec = mysql_query($qry) or die('MySQL Error: '. mysql_error());
    return $exec;
 }

}

Now, i want to replace __construct() with PDO and also change function execute($qry) with PDO.

As of now i have included PDO.php class with DB connection as require_once in index.php but in this way i feel that Model is not getting used at all.

I am using PIP framework for PHP to use MVC. Please let me know how can i use PDO here. Link to PIP framework is HERE