/** @brief Adds new sort parameter or substitutes existing one.
*
* @param $current_value [in] current sort order value.
* @param $sort_param [in] new sort parameter
* @param $order [in] sort order
*
* @return copy of current query.
*/
private function internal_add_sort($current_value, $sort_param, $order, $feed = null)
{
if ($sort_param == '') {
$sort_param = null;
}
if (!is_null($sort_param)) {
if (strncmp('afs:', $sort_param, 4) == 0) {
AfsSortBuiltins::check_value($sort_param, 'Invalid sort parameter: ');
} elseif (1 != preg_match('/^[a-zA-Z][a-zA-Z0-9_-]*$/', $sort_param)) {
throw new Exception('Invalid sort parameter provided: ' . $sort_param);
}
AfsSortOrder::check_value($order, 'Invalid sort order provided: ');
$new_value = $current_value;
if (is_null($new_value)) {
$new_value = array();
}
$new_value[] = new AfsSortParameter($sort_param, $order, $feed);
} else {
$new_value = array();
}
$this->sort = $new_value;
}