Your user id Stored in Session it can accessed anywhere in the MVC Try this on your controller
public function actionContent(){
$model=new ContentForm;
if(isset($_POST['ContentForm'])) {
$model->attributes=$_POST['ContentForm'];//The post values
$model->userid=Yii::app()->session['iduser'];
if($model->save())
$this->redirect(array('content','contentid'=>$model->contentid));
//$this->redirect(array('content','title'=>$model->title));
//$this->redirect(array('content','content'=>$model->content)); //Why this to many redirects here the first redirect only works here
//$this->redirect(array('content','userid'=>$model->userid));
}
$this->render('content',array('model'=>$model));
}