rendering view in symfony 4

<?php

namespace FrontBundle\Services\ServicePortal;

use FrontBundle\Helper\PortalConstantHelper;
use FrontBundle\Services\ServicePortal\UserManagerService;
use Symfony\Component\Security\Http\EntryPoint\RetryAuthenticationEntryPoint;
use Pimcore\Model\DataObject;
use Pimcore\Controller\FrontendController;
use Symfony\Component\Templating\EngineInterface;


class SlipManagerService
{

    protected $renderer;

    public function __construct(EngineInterface $engineInterface)
    {
        $this->renderer = $engineInterface;
    }

    public function createSlip($orderId)
    {

        $orderObj = \Pimcore\Model\DataObject\ServiceOrder::getById($orderId);
        if (empty($orderObj)) {
            return false;
        }

        $packingSlipPdf = $this->createPackingSlipPdf($orderObj);
    }

    public function createPackingSlipPdf(\Pimcore\Model\DataObject\ServiceOrder $myObject)
    {
        $itemList = [];
        $count = count($myObject->getChildren());

        for ($i = 0; $i < $count; $i++) {
            $itemList[$i]['orderID'] = $myObject->getId();
            $itemList[$i]['prefix'] = $myObject->getChildren()[$i]->getAttachedParts()->getPrefix();
            $itemList[$i]['factoryCode'] = $myObject->getChildren()[$i]->getAttachedParts()->getFactoryCode();
            $itemList[$i]['description'] = $myObject->getChildren()[$i]->getAttachedParts()->getDescription();
            $itemList[$i]['price'] = $myObject->getChildren()[$i]->getAttachedParts()->getPrice();
            $itemList[$i]['availableQuantity'] = $myObject->getChildren()[$i]->getAttachedParts()->getAvailableQuantity();
            $itemList[$i]['quantity'] = $myObject->getChildren()[$i]->getOrderedQuantity();
            $itemList[$i]['postCode'] = $myObject->getPostCode();
            $itemList[$i]['city'] = $myObject->getCity();
            $itemList[$i]['country'] = $myObject->getCountry();
            $itemList[$i]['street'] = $myObject->getStreet();
            $itemList[$i]['streetNumber'] = $myObject->getStreetNumber();
            $itemList[$i]['phoneNumber'] = $myObject->getPhoneNumber();
            $itemList[$i]['mobileNumber'] = $myObject->getMobileNumber();
        }
        $pdfInstance = (\Pimcore\Web2Print\Processor::getInstance());
        $pdfInstance->setOptions("--print-media-type --page-size A3 ");
        $html = $this->renderer->render('/service-portal/admin/slipPdf.html.php', ["itemList" => $itemList]);
        $pdf = $pdfInstance->getPdfFromString($html);

        $asset = new \Pimcore\Model\Asset();
        $asset->setFilename('sas' . uniqid() . '.pdf');
        $parentFolder = \Pimcore\Model\Asset\Service::createFolderByPath(PortalConstantHelper::PACKING_SLIP_PDF_ASSET_FOLDER);
        $asset->setParent($parentFolder);
        $asset->setData($pdf);
        $asset->save();
    }
}