+ $rs1->sort($sort_expr);
+
+or create a new sorted resultset:
+
+ $rs2 = $rs1->sort($sort_expr);
+
+The sort expression has the same format as described in the I<yaz_client> documentation. For example:
+
+ $rs1->sort('1=4 id');
+
+will sort thr results by title, in a case insensitive way, in descending order, while
+
+ $rs1->sort('1=4 a');
+
+will sort ascending by titles.