code: public static function findPost($strKey)
  	{
  		if (isset($_POST[$strKey]))
  		{
  			return $_POST[$strKey];
  		}
  
  		$request = System::getContainer()->get('request_stack')->getMasterRequest();
  
  		// Return if the session has not been started before
  		if ($request === null || !$request->hasPreviousSession())
  		{
  			return null;
  		}
  
  		if (isset($_SESSION['FORM_DATA'][$strKey]))
  		{
  			return ($strKey == 'FORM_SUBMIT') ? preg_replace('/^auto_/i', '', $_SESSION['FORM_DATA'][$strKey]) : $_SESSION['FORM_DATA'][$strKey];
  		}
  
  		return null;
  	}
docs: Fallback to the session form data if there is no post data
  
  @param string $strKey The variable name
  
  @return mixed The variable value