Yii 行为是干什么的？
Yii行为是事件的升级版，所有的行为都是Behavior的子类，其作用是将相似事件句柄放在一起，在行为执行“attach()”方法的时候会将“events()”方法中返回的事件句柄进行绑定，这样做达到方面管理和扩展的目的。
示例代码
/**
* Raised right BEFORE the application processes the request.
* @param CEvent $event the event parameter
*/
public function onBeginRequest($event)
{
$this->raiseEvent('onBeginRequest',$event);
}
/**
* Runs the application.
* This method loads static application components. Derived classes usually overrides this
* method to do more application-specific tasks.
* Remember to call the parent implementation so that static application components are loaded.
*/
public function run()
{
if($this->hasEventHandler('onBeginRequest'))
$this->onBeginRequest(new CEvent($this));
$this->processRequest();
if($this->hasEventHandler('onEndRequest'))
$this->onEndRequest(new CEvent($this));
} 
