gistfile1.php

<?php

class PageController extends Controller
{
    ...

    /**
     *
     *
     * @throws \eZ\Publish\API\Repository\Exceptions\NotFoundException
     *
     * @param mixed $id
     * @param array $params
     * @param array $cacheSettings
     *
     * @return Response
     */
    public function viewBlockById( $id, array $params = array(), array $cacheSettings = array() )
    {
        $locationId = $this->pageService->getLocationIdByBlockId( $id );
        $location = $this->getRepository()->getLocationService()->loadLocation( $locationId );
        $content = $this->getRepository()->getContentService()->loadContent( $location->contentId );

        foreach ( $content->fields as $field )
        {
            if ( $field instanceof Value )
            {
                foreach ( $field->page->zones as $zone )
                {
                    foreach ( $zone->blocks as $block )
                    {
                        if ( $block->id === $id )
                        {
                            return $this->viewBlock(
                                $block,
                                $params,
                                $cacheSettings
                            );
                        }
                    }
                }
            }
        }

        throw new NotFoundException( "Block", $id );
    }
}