yii2.0 修改header屬性值

use yii\web\Response;

//修改content-type值
$response = \Yii::$app->response;
$response->format = Response::FORMAT_RAW;
$response->headers->add('Content-Type', 'image/png');

或者：

$response = Yii::$app->response;
$response->format = \yii\web\Response::FORMAT_JSON;
$response->data = ['message' => 'hello world'];