Analysis of filter usage in Yii controller

public function filters()
{
  return array(
    'accessControl', // perform access control for CRUD operations
    'postOnly + delete', // we only allow deletion via POST request
    'projectContext +create index admin',
  );
}

public function filterProjectContext($filterChain)
{
  $prijectId = null;
  if(isset($_POST['pid'])){
    $projectId = $_POST['pid'];
  }elseif(isset($_GET['pid'])){
    $projectId = $_GET['pid'];
  }
  $this->loadProject($projectId);
  $filterChain->run();
}
public function loadProject($projectid)
{
  if($this->_project === null){
    $this->_project = Project::model()->findbyPK($projectid);
    if($this->_project === null){
      throw new CHttpException(404,'请求和项目没找到！');
    }
  }
  return $this->_project;
}