+ /**
+ * Returns data for HTTP conditional request mechanisms.
+ *
+ * @since 1.26
+ * @param string $condition Condition being queried:
+ * - last-modified: Return a timestamp representing the maximum of the
+ * last-modified dates for all resources involved in the request. See
+ * RFC 7232 § 2.2 for semantics.
+ * - etag: Return an entity-tag representing the state of all resources involved
+ * in the request. Quotes must be included. See RFC 7232 § 2.3 for semantics.
+ * @return string|boolean|null As described above, or null if no value is available.
+ */
+ public function getConditionalRequestData( $condition ) {
+ return null;
+ }
+