Forwards the request to another controller.
string|NULL $controller: The controller name (a string like BlogBundle:Post:index).
array $attributes: An array of request attributes.
array $query: An array of request query parameters.
public function forward($controller, array $attributes = array(), array $query = array()) {
$subrequest = $this
->setupSubrequest($controller, $attributes, $query);
return $this
->handle($subrequest, HttpKernelInterface::SUB_REQUEST);
}