core/Mysql.php
public function beginTransaction()
    {
        if (!$this->transactionCounter++) {
            return $this->pdo->beginTransaction();
        }
        $this->pdo->exec('SAVEPOINT trans' . $this->transactionCounter);
        return $this->transactionCounter >= 0;
    }
public function beginTransaction()
    {
        if (!$this->transactionCounter++) {
            return $this->pdo->beginTransaction();
        }
        $this->pdo->exec('SAVEPOINT trans' . $this->transactionCounter);
        return $this->transactionCounter >= 0;
    }
开启事务
@return bool