yii\web\HeadersAlreadySentException: Headers already sent.

[ChaDmiS]

If you decide to use this solution, as I did, then you may encounter an error resending headers yii\web\HeadersAlreadySentException: Headers already sent.

The thing is that licson/libSSE-php itself sends headers via Symfony StreamedResponse https://github.com/licson/libSSE-php/blob/master/src/SSE.php#L266, without affecting Yii in any way.

This solution does not take this into account.

Yii sends headers here https://github.com/yiisoft/yii2/blob/master/framework/web/Response.php#L346

So I just told Yii that the response has already been sent, something like this:

Yii::$app->response->isSent = true;

Full example:

Yii::$app->response->isSent = true;
$sse = Yii::$app->sse;
$sse->addEventListener ('message', new MessageEventHandler ());
$sse->start();

The solution, of course, is straightforward, but it works :)

[raezon]

it does work

[donal56]

Thanks, it worked