How can I modify the response formatting itself? - yii2

Question

In an action I need to responde with some XML. I use Response::FORMAT_XML for that, which works fine.
// In a controller:
public static function actionFetchData() {
Yii::$app->response->format = Response::FORMAT_XML;
return [
'a' => 'b',
['c', 'd'],
'e' => ['f', 'g']
];
}
Result in Browser:
<?xml version="1.0" encoding="UTF-8"?>
<response>
<a>b</a>
<item>
<item>c</item>
<item>d</item>
</item>
<e>
<item>f</item>
<item>g</item>
</e>
</response>
However, I'd like to change the root tags name from response to data. This should be possible since XmlResponseFormatter, which gets used to render the XML, has the property rootTag. How can I do that?
Or in general: How can I change the settings of a formatter (also JSON or whatever)?

Answer 1

If you want to change format specific to particular action then use :.
Yii::$app->response->format = Response::FORMAT_XML;
Yii::$app->response->formatters = [
'xml' => [
'class' => 'yii\web\XmlResponseFormatter',
'rootTag' => 'data',
],
];
return [
'a' => 'b',
['c', 'd'],
'e' => ['f', 'g']
];

Answer 2

One way is to create an own formatter object for XML. Reason: In Yii::$app->response the formmatter is not present within the action - it will be created later, when the response gets rendered, what it too late to modify it. But we can create a new formatter and set it as the formatter for XML. This is a valid option.
public static function actionMetaInfo($docId) {
$formatter = new XmlResponseFormatter([
'rootTag' => 'data',
'itemTag' => 'unnamed',
]);
Yii::$app->response->formatters[Response::FORMAT_XML] = $formatter;
Yii::$app->response->format = Response::FORMAT_XML;
return [
'a' => 'b',
['c', 'd'],
'e' => ['f', 'g']
];
}
Output now:
<?xml version="1.0" encoding="UTF-8"?>
<data>
<a>b</a>
<unnamed>
<unnamed>c</unnamed>
<unnamed>d</unnamed>
</unnamed>
<e>
<unnamed>f</unnamed>
<unnamed>g</unnamed>
</e>
</data>
Here I changed the itemTag as well. This way, we can also modify other Formatter's properties (e.g. also in JsonResponseFormatter).

Answer 3

If you want to modify XML response formatter for all your application, you should simply add this to your configuration file :
'components' => [
'response' => [
'formatters' => [
'xml' => [
'class' => 'yii\web\XmlResponseFormatter',
'rootTag' => 'data',
],
],
],
],