A sample frontpage controller which picks a random banner image from a list of related objects

DefaultController.php

    public function indexAction( $locationId = 2 )
    {
        $response = new Response;
        $response = $this->cacheResponse( $response, $locationId, 10 );

        /** @var $repository \eZ\Publish\API\Repository\Repository */
        $repository = $this->getRepository();
        $contentService = $repository->getContentService();
        $locationService = $repository->getLocationService();

        $location = $locationService->loadLocation( $locationId );
        $content = $contentService->loadContent( $location->contentId );

        // get relations of the current version
        $versionInfo = $contentService->loadVersionInfo( $content->contentInfo );
        $relations = $contentService->loadRelations( $versionInfo );

        $related = null;
        /**  @var $random \eZ\Publish\API\Repository\Values\Content\Relation */
        if ( count( $relations ) )
        {
            $random = $relations[array_rand( $relations )];
            $related = $contentService->loadContent( $random->destinationContentInfo->id );
        }

        return $this->render(
                    "WebmanufakturSiteFrbBundle:full:frb_folder_section.html.twig",
                        array(
                            'content' => $content,
                            'related' => $related
                        ),
                        $response
        );
    }