如果出现错误，则PDO会引发一个异常，您可以捕获该异常.用try catch包装您的代码，并且应该捕获所有异常.

If there's an error then PDO will throw an exception which you can catch. Wrap your code with a try catch and that should catch any exceptions.

try {
    $rs = $db->prepare('SELECT * FROM foo');
    $rs->execute();
    $foo = $rs->fetchAll();
} catch (Exception $e) {
    echo 'Error: '.$e->getMessage();
}