I needed to send a number of Cache-* and Content-* header while working on a project where download was done in my own DowloadController.
I’m using PHP Framework Neos Flow for this project.
Since Neos Flow 6, the PSR-7 has been implemented and I can no longer set it directly on the $this->response object.
Instead, headers are added to a Component being executed in the rendering. So, adding a header with a value is done like this
$this->response->setComponentParameter(SetHeaderComponent::class, 'Cache-control', 'private');
Inside your action – adding several is one per line