ErrorException [致命错误]：找不到类'请求'

Question

我收到此错误：

ErrorException [ Fatal Error ]: Class 'Request' not found

APPPATH\bootstrap.php [ 197 ]

/** 
* Execute the main request. A source of the URI can be passed, eg: $_SERVER['PATH_INFO'].
* If no source is specified, the URI will be automatically detected. 
*/  
echo Request::instance()  
->execute()  
->send_headers()  
->response;  
} 

{PHP internal call} » Kohana_Core::shutdown_handler()

知道这里发生了什么吗？