Elgg\Http\ResponseFactory::setHeader PHP Method

Sets headers to apply to all responses being sent

public setHeader ( string $name, string $value, boolean $replace = true ) : void
$name	string	Header name
$value	string	Header value
$replace	boolean	Replace existing headers
return	void

    public function setHeader($name, $value, $replace = true)
    {
        $this->headers->set($name, $value, $replace);
    }

ResponseFactory