/**
* Method to get an additional URL parameter (if it exists) to be added to
* all pagination class generated links.
*
* @param string $key The name of the URL parameter for which to get the value.
*
* @return mixed The value if it exists or null if it does not.
*
* @since 1.6
*/
public function getAdditionalUrlParam($key)
{
return $this->additionalUrlParams[$key] ?? null;
}