If you want the whole transaction be rolled back automatically as soon as an error occurs, you could just re-throw the exception from B 's exception handler when called from some specific locations (eg. from A() ):

function A(){
   ...
   $this->B(true);
   ...
}

/*

* @param B boolean Throw an exception if the transaction is rolled back
* /

function B($rethrow) {
    $transaction=Yii::app()->db->beginTransaction();
    try {
        //do something
        $transaction->commit();
    } catch(Exception $e) {
        $transaction->rollBack();
        if ($rethrow) throw $e;
    }
}

Now I understand you actually just want your wrapper to detect if a transaction is already in progress, and in this case not start the transaction.
Therefore you do not really need the NestedPDO class. You could create a class like this instead:

class SingleTransactionManager extends PDO {
    private $nestingDepth = 0;

    public function beginTransaction() {
        if(!$this->nestingDepth++ == 0) {
            parent::beginTransaction();
        } // else do nothing
    }
    public function commit() {
        $this->nestingDepth--;
        if (--$this->nestingDepth == 0) {
            parent::commit();
        } // else do nothing
    }

    public function rollback() {
        parent::rollback();
        if (--$this->nestingDepth > 0) {
            $this->nestingDepth = 0;
            throw new Exception(); // so as to interrupt outer the transaction ASAP, which has become pointless
        }

    }
}

根据@RandomSeed的回答，我创建了一个默认Yii交易处理的'drop in'：

$connection = Yii::app()->db;
$transaction=$connection->beginTransaction();
try
{
   $connection->createCommand($sql1)->execute();
   $connection->createCommand($sql2)->execute();
   //.... other SQL executions
   $transaction->commit();
}
catch(Exception $e)
{
   $transaction->rollback();
}

这是我的SingleTransactionManager类：

class SingleTransactionManager extends CComponent 
{
    // The current transaction level.
    private $transLevel = 0;

    // The CDbConnection object that should be wrapped
    public $dbConnection;

    public function init()
    {
        if($this->dbConnection===null)
            throw new Exception('Property `dbConnection` must be set.');

        $this->dbConnection=$this->evaluateExpression($this->dbConnection);
    }
    // We only start a transaction if we're the first doing so
    public function beginTransaction() {
        if($this->transLevel == 0) {
            $transaction = parent::beginTransaction();
        } else {
            $transaction = new SingleTransactionManager_Transaction($this->dbConnection, false);
        }
        // always increase transaction level:
        $this->transLevel++;

        return $transaction;
    }

    public function __call($name, $parameters)
    {
        return call_user_func_array(array($this->dbConnection, $name), $parameters);
    }
}

class SingleTransactionManager_Transaction extends CDbTransaction
{
    // boolean, whether this instance 'really' started the transaction
    private $_startedTransaction;

    public function __construct(CDbConnection $connection, $startedTransaction = false)
    {
        $this->_startedTransaction = $startedTransaction;
        parent::__construct($connection);
        $this->setActive($startedTransaction);
    }

    // We only commit a transaction if we've started the transaction
    public function commit() {
        if($this->_startedTransaction)
            parent::commit();
    }

    // We only rollback a transaction if we've started the transaction
    // else throw an Exception to revert parent transactions/take adquate action
    public function rollback() {
        if($this->_startedTransaction)
            parent::rollback();
        else
            throw new Exception('Child transaction rolled back!');
    }
}

此类“ Package ”主数据库连接，应在配置中将其声明为组件，如下所示：

'components'=>array(

    // database
    'db'=>array(
        'class' => 'CDbConnection',
        // using mysql
        'connectionString'=>'....',
        'username'=>'...',
        'password'=>'....',
    ),

    // database
    'singleTransaction'=>array(
        'class' => 'pathToComponents.db.SingleTransactionManager',
        'dbConnection' => 'Yii::app()->db'
    )

请注意，dbConnection属性应该是master数据库联机的表示式。现在，当巢状Try catch区块中的巢状交易时，您可以在例如巢状交易3中建立错误，而1和2上的巢状交易也会回复。
测试代码：

$connection = Yii::app()->singleTransaction;

$connection->createCommand('CREATE TABLE IF NOT EXISTS `test_transactions` (
  `number` int(10) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;')->execute();

$connection->createCommand('TRUNCATE TABLE `test_transactions`;')->execute();

testNesting(4, 3, 1);

echo '<br>';
echo 'Rows:';
echo '<br>';
$rows = $connection->createCommand('SELECT * FROM `test_transactions`')->queryAll();
if($rows)
{
    foreach($rows as $row)
    {
        print_r($row);
    }
}
else
    echo 'Table is empty!';

function testNesting(int $total, int $createErrorIn = null, int $current = 1)
{
    if($current>=$total)
        return;

    $connection = Yii::app()->singleTransaction;
    $indent = str_repeat('&nbsp;', ($current*4));

    echo $indent.'Transaction '.$current;
    echo '<br>';
    $transaction=$connection->beginTransaction();
    try
    {
        // create nonexisting columnname when we need to create an error in this nested transaction
        $columnname = 'number'.($createErrorIn===$current ? 'rr' : '');
        $connection->createCommand('INSERT INTO `test_transactions` (`'.$columnname.'`) VALUES ('.$current.')')->execute();

        testNesting($total, $createErrorIn, ($current+1));

        $transaction->commit();
    }
    catch(Exception $e)
    {
        echo $indent.'Exception';
        echo '<br>';
        echo $indent.$e->getMessage();
        echo '<br>';
        $transaction->rollback();
    }
}

产生以下输出：

Transaction 1
        Transaction 2
            Transaction 3
            Exception
            CDbCommand failed to execute the SQL statement: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'numberrr' in 'field list'. The SQL statement executed was: INSERT INTO `test_transactions` (`numberrr`) VALUES (3)
        Exception
        Child transaction rolled back!
    Exception
    Child transaction rolled back!

Rows:
Table is empty!

恕我直言，在应用程序代码中模拟“嵌套事务”的想法是一种反模式。在应用程序中有许多不可能解决的异常情况（请参阅我对https://stackoverflow.com/a/319939/20860的回答）。
在PHP中，最好保持简单。工作被自然地组织成请求，所以使用请求作为事务作用域。

• 在调用任何模型类之前，在控制器级别启动一个事务。
• 让模型在发生任何错误时抛出异常。
• 在控制器级别捕获异常，并在必要时回滚。
• 如果未捕获到异常，则提交。

忘记所有关于事务级别的废话，模型不应该启动、提交或回滚任何事务。