/**
* Returns the full URL to the previous page of results, or null.
*
* @return string|null
*/
public function getPreviousPageURI(string
$group = 'default', bool
$returnObject = false
) { $this->
ensureGroup($group);
$first =
$this->
getFirstPage($group);
$curr =
$this->
getCurrentPage($group);
$page = null;
if (!
empty($first) && !
empty($curr) &&
$first ===
$curr) { return null;
} if ($first <
$curr) { $page =
$curr - 1;
}