extension=php_pdo.dll
extension=php_pdo_mysql.dll

$username = "root";
$password = "root";
$pdo = new PDO(
        'mysql:host=localhost;dbname=iiidb',
        $username,
        $password,
        array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));

try {
    $pdo = new PDO(
        'mysql:host=localhost;dbname=iiidb',
        $username,
        $password,
        array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));

    // add
    $pdo -> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // select~ statement
    ....
} catch (PDOException $e) {
    echo $e->getMessage();
}