unable to change reponse header

guys I’m trying generate XML using php but I’m not able to change response header to xml


        \Yii::$app->response->format = \yii\web\Response::FORMAT_XML;

        $date = date('Y-m-d');

        $homeurl = $_SERVER['HTTP_HOST'] . \Yii::$app->homeUrl;

        $sitemap = new \SimpleXMLElement('<urlset/>');

        $animelist = Anime::find()->all();

        foreach ($animelist as $anm) {

            $lurl = $sitemap->addChild('url');

            $lurl->addChild('loc',"$homeurl$anm->url/");

            $lurl->addChild('changefreq',"daily");

            $lurl->addChild('priority',"0.8");

             } 

        print($sitemap->asXML());

This topic is for the first version, not for the second