Doctrine\DBAL\Connection::fetchColumn PHP Method

    public function fetchColumn($statement, array $params = array(), $column = 0, array $types = array())
    {
        return $this->executeQuery($statement, $params, $types)->fetchColumn($column);
    }

 protected function doStart($parentId)
 {
     $this->conn->beginTransaction();
     $platform = $this->conn->getDatabasePlatform();
     $variables = $this->variables;
     $executionNextPollDate = null;
     if (isset($variables['batchWaitInterval'])) {
         if (!$variables['batchWaitInterval'] instanceof \DateInterval) {
             throw new \ezcWorkflowExecutionException("Specified batch waiting interval has to be instance of DateInterval!");
         }
         $executionNextPollDate = new \DateTime("now");
         $executionNextPollDate->add($variables['batchWaitInterval']);
         $executionNextPollDate = $executionNextPollDate->format($platform->getDateTimeFormatString());
     }
     $serializer = $this->options->getSerializer();
     $now = new \DateTime("now");
     $data = array('workflow_id' => (int) $this->workflow->id, 'execution_parent' => $parentId, 'execution_started' => $now->format($platform->getDateTimeFormatString()), 'execution_variables' => $serializer->serialize($variables), 'execution_waiting_for' => $serializer->serialize($this->waitingFor), 'execution_threads' => $serializer->serialize($this->threads), 'execution_next_thread_id' => (int) $this->nextThreadId, 'execution_next_poll_date' => $executionNextPollDate);
     if ($platform->prefersSequences()) {
         $data['execution_id'] = (int) $this->conn->fetchColumn($platform->getSequenceNextValSQL($this->options->executionSequence()));
         $this->id = $data['execution_id'];
     }
     $this->conn->insert($this->options->executionTable(), $data);
     // execution_id
     if (!$platform->prefersSequences()) {
         $this->id = (int) $this->conn->lastInsertId();
     }
 }