QuickBooks/WebConnector/Queue.php
public function exists($action, $ident, $user = null)
	{
		if ($this->_driver)
		{
			// Use the default user (provided in __construct) if none is given
			if (!$user)
			{
				$user = $this->_user;
			}			
			
			return $this->_driver->queueExists($user, $action, $ident);
		}
		
		return null;
	}
public function exists($action, $ident, $user = null)
	{
		if ($this->_driver)
		{
			// Use the default user (provided in __construct) if none is given
			if (!$user)
			{
				$user = $this->_user;
			}			
			
			return $this->_driver->queueExists($user, $action, $ident);
		}
		
		return null;
	}
Tell whether or not an action/ident already exists in the queue

@param string $action	An action to be performed within QuickBooks
@param mixed $ident		A unique identifier (if required) for the record being operated on
@param string $user		The username of the user to check if the queued item exists for
@return boolean			Whether or not that action/ident tuple is already in the queue