覆蓋特定操作的 Content-Type

Created: November-22, 2018

用例：只有一個應該按原樣返回普通（文字）內容的操作：

public function actionAsXML()
{
    $this->layout = false;
    Yii::$app->response->format = Response::FORMAT_XML;

    return ['aaa' => [1, 2, 3, 4]];;
}

預定義的響應格式為：

FORMAT_HTML
FORMAT_XML
FORMAT_JSON
FORMAT_JSONP
FORMAT_RAW

對於 text/plain 沒有開箱即用的 mime 型別，請改用：

public function actionPlainText()
{
    $this->layout = false;
    Yii::$app->response->format = Response::FORMAT_RAW;
    Yii::$app->response->headers->add('Content-Type', 'text/plain');

    return $this->render('plain-text'); // outputs template as plain text
}