abstract class Tx_XXX_Controller_AbstractMultiStepFormController extends Tx_Extbase_MVC_Controller_ActionController {
 
	/**
	 * Session storage key used
	 * @var string
	 */
	protected $sessionDataStorageKey;
 
	/**
	 * The session data container
	 * @var array
	 */
	protected $sessionData = array();
 
	/**
	 * The actual form data
	 * @var array
	 */
	protected $formData;
 
	/**
	 * A list of action names that have been passed successfully.
	 * @var array
	 */
	protected $passedActionMethodNames;
 
	/**
	 * A list of action names that have to be passed before the final action can be executed.
	 * @var array
	 */
	protected $mandatoryActionMethodNames;
 
	/**
	 * The action methode name of the first action.
	 * @var string
	 */
	protected $firstActionMethodName;
 
	/**
	 * The action methode name of the first action.
	 * @var string
	 */
	protected $finalActionMethodName;
 
	/**
	 * Handles session/argument interaction to ensure correct validation. Furthermore
	 * takes care of mandatory actions.
	 * @return void
	 */
	protected function initializeAction() {
		$this->loadSessionData();
 
		if ($this->isFinalAction() && !$this->passedMandatoryActions()) {
			$this->redirect($this->firstActionMethodName);
		}
 
		if ($this->formData === NULL) {
			if(!$this->isFirstAction()) {
				$this->redirect($this->firstActionMethodName);
			} else {
				$this->formData = array();
			}
		}
 
		$requestArguments = $this->request->getArguments();
 
		foreach ($this->arguments->getArgumentNames() as $argumentName) {
			if (array_key_exists($argumentName, $requestArguments)) {
				$this->formData[$argumentName] = $requestArguments[$argumentName];
			} else {
				if(array_key_exists($argumentName, $this->formData)) {
					$requestArguments[$argumentName] = (String)$this->formData[$argumentName];
					$_POST['tx_' . strtolower($this->extensionName) .
						'_' . strtolower($this->request->getPluginName())][$argumentName] =
						(String)$this->formData[$argumentName];
				}
			}
		}
 
		$this->request->setArguments($requestArguments);
 
		$this->storeSessionData();
	}
 
	/**
	 * We use initializeView to determin if a certain action has been reached
	 * and all it's validation has been passed successful.
	 * @return void
	 */
	protected function initializeView() {
		$this->passedActionMethodNames[$this->actionMethodName] = TRUE;
		$this->storeSessionData();
 
	}
 
	/**
	 * Returns if this is the first action.
	 * @return boolean
	 */
	protected function isFirstAction() {
		return $this->actionMethodName === $this->firstActionMethodName;
	}
 
	/**
	 * Returns if this is the final action.
	 * @return boolean
	 */
	protected function isFinalAction() {
		return $this->actionMethodName === $this->finalActionMethodName;
	}
 
	/**
	 * Checks if all mandatory actions have been passed.
	 * @return boolean
	 */
	protected function passedMandatoryActions() {
		foreach($this->mandatoryActionMethodNames as $mandatoryActionMethodeName) {
			if ($this->passedActionMethodNames[$mandatoryActionMethodeName] === NULL) {
				return FALSE;
			}
		}
		return TRUE;
	}
 
	/**
	 * Loads data from session and populates formData and passedActionMethodeNames.
	 * @return void
	 */
	protected function loadSessionData() {
		$this->sessionData =
			$GLOBALS['TSFE']->fe_user->getKey('ses', $this->sessionDataStorageKey);
 
		$this->formData = $this->sessionData['formData'];
		$this->passedActionMethodNames = $this->sessionData['passedActionMethodNames'];
	}
 
	/**
	 * Stores data to session. Including formData and passedActionMethodeNames.
	 * @return void
	 */
	protected function storeSessionData() {
		$this->sessionData['formData'] = $this->formData;
		$this->sessionData['passedActionMethodNames'] = $this->passedActionMethodNames;
 
		$GLOBALS['TSFE']->fe_user->setKey('ses', $this->sessionDataStorageKey,
			$this->sessionData);
 
		$GLOBALS['TSFE']->fe_user->storeSessionData();
	}
 
	protected function clearSessionData() {
		$this->sessionData = array();
 
		$GLOBALS['TSFE']->fe_user->setKey('ses', $this->sessionDataStorageKey,
			$this->sessionData);
 
		$GLOBALS['TSFE']->fe_user->storeSessionData();
	}
 
}

class Tx_XXX_Controller_WhateverController extends Tx_XXX_Controller_AbstractMultiStepFormController {
 
	protected $sessionDataStorageKey = 'tx_xxx_whatever_form';
 
	protected $firstActionMethodName = 'step1Action';
	protected $finalActionMethodName = 'submitAction';
 
	protected $mandatoryActionMethodNames = array('step1Action',
		'step2Action',
		'step3Action',
		'summaryAction');
 
	/**
	 * @param string $name
	 * @param string $firstname
	 * @return string A html form
	 */
	public function step1Action($name = NULL, $firstname) {
		$this->view->assignMultiple(array(
			'name' => $name,
			'firstname' => $firstname);
	}
 
	/**
	 * @param string $name
	 * @param string $firstname
	 * @param string $email
	 * @param string $street
	 * @param string $streetNumber
	 * @validate $name notEmpty;
	 * @validate $firstname notEmpty;
	 * @return string A html form
	 */
	public function step2Action($name, $firstname $email = NULL, $street = NULL,
		 $streetNumber = NULL) {
 
		$this->view->assignMultiple(array(
			'email' => $email,
			'street' => $street,
			'streetNumber' => $streetNumber));
	}
 
	/**
	 * @param string $email
	 * @param string $street
	 * @param string $streetNumber
	 * @param string $zip
	 * @param string $location
	 * @validate $email notEmpty;
	 * @validate $street notEmpty;
	 * @validate $streetNumber notEmpty;
	 */
	public function step3Action($email, 	$street, $streetNumber,
		$zip = NULL, $location = NULL) {
 
		$this->view->assignMultiple(array(
			'zip' => $zip,
			'location' => $location);
	}
 
	/**
	 * @param string $zip
	 * @param string $location
	 * @validate $zip notEmpty;
	 * @validate $location notEmpty;
	 */
	public function summary($zip, $location) {
		$this->view->assign('formData' => $this->formData);
	}
 
	public function submitAction() {
		// do something ...
 
	}	
 
}