Here's the original code and my modifications. It works in my testing. Hope this helps.

Thanks, Brendan
http://www.bsfmedia.com

ORIGINAL CODE:
function photosets_getPhotos($photoset_id, $extras = NULL, $privacy_filter = NULL)
{
/* http://www.flickr.com/services/api/flickr.photosets.getPhotos.html */
$this->request("flickr.photosets.getPhotos", array("photoset_id" => $photoset_id, "extras" => $extras, "privacy_filter" => $privacy_filter));
return $this->parsed_response ? $this->parsed_response['photoset'] : false;
}

REVISED CODE:
function photosets_getPhotos($photoset_id, $extras = NULL, $privacy_filter = NULL, $per_page = NULL, $page = NULL)
{
/* http://www.flickr.com/services/api/flickr.photosets.getPhotos.html */
$this->request("flickr.photosets.getPhotos", array("photoset_id" => $photoset_id, "extras" => $extras, "privacy_filter" => $privacy_filter, "per_page" => $per_page, "page" => $page));
return $this->parsed_response ? $this->parsed_response['photoset'] : false;
}

CALLED VIA PHP:
$photos = $f->photosets_getPhotos($photoset_id, NULL, NULL, 1);