如何在zend框架1中处理无效的数据库

Question

我正在使用Zend框架1.12.我有一个基于ajax的UI，它将用户帐户信息（存储在master数据库中）发送到控制器。每个用户帐户都有其相关的DB。但是当我选择没有相关数据库的用户时，控制器会发送应用程序错误。我希望将一些消息发送到UI。

private function _initDB()
{
    global $databaseip, $username, $password;
    try {
         // I can access this scope with valid db name   
         // for multi user && multi db              
         $this->_pdo = new Zend_Db_Adapter_Pdo_Mysql(
            array(
                'host' => $databaseip,
                'username' => $username,
                'password' => $password,
                'dbname' => $this->_dbname,
            )
        );

    } catch (Zend_Exception $e) {
        // I want some message to be passed to UI.

        // can't access this scope with invalid dbname
        // as users list stores in master database
        // may be db-admin deleted database of that user
        // but forgot to delete that user from master-users database
    }
}   

提前致谢：