public function writefile($filename,$txt){
    $myfile = fopen($_SERVER['DOCUMENT_ROOT'].'/'.$filename, "a") or die("Unable to open file!");
    fwrite($myfile, $txt);
    fclose($myfile);
}


/**
* 实例化（分层）控制器 格式：[模块名/]控制器名
* @access public
* @param string $name 资源地址
* @param string $layer 控制层名称
* @param bool $appendSuffix 是否添加类名后缀
* @param string $empty 空控制器名称
* @return object
* @throws ClassNotFoundException
*/
public static function controller($name, $layer = 'controller', $appendSuffix = false, $empty = '')
{
list($module, $class) = self::getModuleAndClass($name, $layer, $appendSuffix);

if (class_exists($class)) {
return App::invokeClass($class);
}

if ($empty) {
$emptyClass = self::parseClass($module, $layer, $empty, $appendSuffix);
if (class_exists($emptyClass)) {
return new $emptyClass(Request::instance());
}
}

throw new ClassNotFoundException(‘class not exists:’ . $class, $class);
}