+=item MEMCACHED_CALLBACK_GET_FAILURE
+
+This function implements the read through cache behavior. On failure of retrieval this callback will be called.
+You are responsible for populating the result object provided. This result object will then be stored in the server and
+returned to the calling process. You must clone the memcached_st in order to
+make use of it. The value will be stored only if you return
+MEMCACHED_SUCCESS or MEMCACHED_BUFFERED. Returning MEMCACHED_BUFFERED will
+cause the object to be buffered and not sent immediatly (if this is the default behavior based on your connection setup this will happen automatically).
+
+The prototype for this is:
+memcached_return (*memcached_trigger_key)(memcached_st *ptr, char *key, size_t key_length, memcached_result_st *result);
+
+=item MEMCACHED_CALLBACK_DELETE_TRIGGER
+
+This function implements a trigger upon successful deletion of a key. The memcached_st structure will need to be cloned
+in order to make use of it.
+
+The prototype for this is:
+typedef memcached_return (*memcached_trigger_delete_key)(memcached_st *ptr, char *key, size_t key_length);
+