core-bundle/src/Resources/contao/library/Contao/Controller.php
public static function addToUrl($strRequest, $blnAddRef=true, $arrUnset=array())
	{
		/** @var Query $query */
		$query = new Query(Environment::get('queryString'));

		// Remove the request token and referer ID
		$query = $query->withoutPairs(array_merge(array('rt', 'ref'), $arrUnset));

		// Merge the request string to be added
		$query = $query->merge(str_replace('&amp;', '&', $strRequest));

		// Add the referer ID
		if (isset($_GET['ref']) || ($strRequest != '' && $blnAddRef))
		{
			$query = $query->merge('ref=' . System::getContainer()->get('request_stack')->getCurrentRequest()->attributes->get('_contao_referer_id'));
		}

		$uri = $query->getUriComponent();

		// The query parser automatically converts %2B to +, so re-convert it here
		if (strpos($strRequest, '%2B') !== false)
		{
			$uri = str_replace('+', '%2B', $uri);
		}

		return TL_SCRIPT . ampersand($uri);
	}
public static function addToUrl($strRequest, $blnAddRef=true, $arrUnset=array())
	{
		/** @var Query $query */
		$query = new Query(Environment::get('queryString'));

		// Remove the request token and referer ID
		$query = $query->withoutPairs(array_merge(array('rt', 'ref'), $arrUnset));

		// Merge the request string to be added
		$query = $query->merge(str_replace('&amp;', '&', $strRequest));

		// Add the referer ID
		if (isset($_GET['ref']) || ($strRequest != '' && $blnAddRef))
		{
			$query = $query->merge('ref=' . System::getContainer()->get('request_stack')->getCurrentRequest()->attributes->get('_contao_referer_id'));
		}

		$uri = $query->getUriComponent();

		// The query parser automatically converts %2B to +, so re-convert it here
		if (strpos($strRequest, '%2B') !== false)
		{
			$uri = str_replace('+', '%2B', $uri);
		}

		return TL_SCRIPT . ampersand($uri);
	}
Add a request string to the current URL

@param string  $strRequest The string to be added
@param boolean $blnAddRef  Add the referer ID
@param array   $arrUnset   An optional array of keys to unset

@return string The new URL