修改Session 默认值

@@ -22,10 +22,10 @@ class Session
      * @param $namespace
      * @return SessionNamespace
      */
-    static public function start($namespace = 'session_default', $sessionName = '_QIN')
+    static public function start($namespace = 'session_default', $sessionName = null, $domain = null)
     {
         if (self::isSessionStarted() == false || self::$_session == null) {
-            self::$_session = new CacheSession($sessionName);
+            self::$_session = new CacheSession($sessionName, $domain);
             session_start();
         }
         return new SessionNamespace ($namespace);