Clones the current request.
Note that the session is not cloned as duplicated requests are most of the time sub-requests of the main one.
public function __clone() {
$this->query = clone $this->query;
$this->request = clone $this->request;
$this->attributes = clone $this->attributes;
$this->cookies = clone $this->cookies;
$this->files = clone $this->files;
$this->server = clone $this->server;
$this->headers = clone $this->headers;
}