news:news 中间不能有冒号，改写后如下

    return \Yii::createObject([
        'class' => 'yii\web\Response',
        'format' => \yii\web\Response::FORMAT_XML,
        'formatters' => [
            \yii\web\Response::FORMAT_XML => [
                'class' => 'yii\web\XmlResponseFormatter',
                'rootTag' => 'urlset', //根节点
                'itemTag' => 'url', //单元
            ],
        ],
        'data' => [ //要输出的数据
            [
                'loc' => 'http://********',
                'newsnews' => [
                    'newsname' => 'The Example Times',
                ]
            ],
        ],
    ]);