Improved BagOStuff docs.

Change-Id: I01c62de23b73e1bac96aede73cd6995df8ff1221

diff --git a/includes/objectcache/BagOStuff.php b/includes/objectcache/BagOStuff.php
index 03b0d5b..1205ceb 100644 (file)
--- a/includes/objectcache/BagOStuff.php
+++ b/includes/objectcache/BagOStuff.php
@@ -89,7 +89,9 @@ abstract class BagOStuff {
        abstract public function delete( $key, $time = 0 );
 
        /**
-        * Merge changes into the existing cache value (possibly creating a new one)
+        * Merge changes into the existing cache value (possibly creating a new one).
+        * The callback function returns the new value given the current value (possibly false),
+        * and takes the arguments: (this BagOStuff object, cache key, current value).
         *
         * @param $key string
         * @param $callback closure Callback method to be executed