code: protected function initializeSession($formId)
  	{
  		if (Input::post('FORM_SUBMIT') != $formId)
  		{
  			return;
  		}
  
  		$arrMessageBox = array('TL_ERROR', 'TL_CONFIRM', 'TL_INFO');
  		$_SESSION['FORM_DATA'] = \is_array($_SESSION['FORM_DATA']) ? $_SESSION['FORM_DATA'] : array();
  
  		foreach ($arrMessageBox as $tl)
  		{
  			if (\is_array($_SESSION[$formId][$tl]))
  			{
  				$_SESSION[$formId][$tl] = array_unique($_SESSION[$formId][$tl]);
  
  				foreach ($_SESSION[$formId][$tl] as $message)
  				{
  					$objTemplate = new FrontendTemplate('form_message');
  					$objTemplate->message = $message;
  					$objTemplate->class = strtolower($tl);
  
  					$this->Template->fields .= $objTemplate->parse() . "\n";
  				}
  
  				$_SESSION[$formId][$tl] = array();
  			}
  		}
  	}
docs: Initialize the form in the current session
  
  @param string $formId