错误“；类'；Zend_Config_Writer_Xml'；未找到”；当将Zend-libary集成到Co

我复制了一些Zend库，并将它们粘贴到CodeIgniter中的库文件夹中。我试着使用这个代码，没关系：

$this->zend->load('zend/json');
$data = array(
    'name' => 'Killer Whale',
    'email' => 'namnguyen2091@gmail.com',
    'website' => 'baogiadientu.com'
);
// load and encode data
$json = new Zend_Json();
$encode = $json->encode($data);
echo $encode;
//decode with static function
echo '<pre>';
print_r(Zend_Json::decode($encode));
echo '</pre>';

但当我像下面这样编码时，它不起作用，我会得到一个错误：致命错误：在第83行的D:''Programs''examplep''htdocs''baogiadientu''application''controllers''product.php中找不到类"Zend_Config_Writer_Xml"

$this->zend->load('zend/config');
// create the config object
$config = new Zend_Config(array(), true);
$config->production = array();
$config->production->webhost = 'baogiadientu.com';
$config->production->database = array();
$config->production->database->params = array();
$config->production->database->params->host = 'localhost';
$config->production->database->params->username = 'root';
$config->production->database->params->password = '123456';
$config->production->database->params->dbname = 'baogiadientu';
$writer = new Zend_Config_Writer_Xml(); // **here**
echo $writer->toString($config);

我关注这篇文章http://framework.zend.com/manual/2.0/en/modules/zend.config.writer.html.请帮帮我！