*
* @param array $cprefs Client's acceptable type list
* @param array $sprefs Server's offered types
- * @return string
+ * @return string|null
*
* @todo FIXME: Doesn't handle params like 'text/plain; charset=UTF-8'
* XXX: generalize to negotiate other stuff
+ * @todo The function appears unused. Is it worth to keep?
*/
function wfNegotiateType( $cprefs, $sprefs ) {
$combine = [];