I admit, using dump() in a PDF is a bad idea anyways. BUT: it is an easy example leading to a memory leak somewhere.

Assuming: git, PHP, composer and symfony are installed.

• Clone this repository (https://github.com/GenieTim/DomPDF-Twig-dump-error-repro/).
• Install the dependencies with composer install.
• Start the symfony server with symfony server:start.
• Point your browser to https://127.0.0.1:8000/index and wait for PHP to give up, failing to allocate more memory

This repository aims to be a minimum case to reproduce. It was created by:

• symfony new --full
• composer add nucleos/dompdf-bundle
• ./bin/console make:controller
• and a little bit of PHP and Twig code, to be found in src/Controller/IndexController.php and templates/index/index.html.twig