-if(! function_exists('ref_session_write')) {
-function ref_session_write ($id,$data) {
+ return '';
+}
+
+/**
+ * @brief Standard PHP session write callback
+ *
+ * This callback updates the DB-stored session data and/or the expiration depending
+ * on the case. Uses the $session_expire global for existing session, 5 minutes
+ * for newly created session.
+ *
+ * @global bool $session_exists Whether a session with the given id already exists
+ * @global int $session_expire Session expiration delay in seconds
+ * @param string $id Session ID with format: [a-z0-9]{26}
+ * @param string $data Serialized session data
+ * @return boolean Returns false if parameters are missing, true otherwise
+ */
+function ref_session_write($id, $data) {