There is a bug in Symphony 6 that goes along with php version 8.1. We currently had a problem with Sulu 2.4.x, which also ran with php 8.1.

Background: The website was developed and tested on the agency’s web server, which is very performant.

After the website was transferred to the client’s server, the following problems occurred:

_ PDF preview was not rendered (frontend)
_ Images and PDF were not displayed in the backend
_ Images and PDFs could not be deleted in the backend.
_ Changes to templates were not displayed (frontend)

Basically, everything that was cached was not output or only output with a very long delay.

The problem only occurs in prod mode. If you have the option to set the entire system to development mode, the cache is rewritten with every refresh of the page. In this case, everything works perfectly. However, as soon as you switch to productive mode, the problem with the images / documents occurs again.

The assumption is that the cache leads to an error, as all data is read from the cache in production mode. We have installed the CMS Sulu with the current version on our managed servers and it works perfectly. After comparing the PHP info output, we discovered that the opCache module is missing on the customer server.

After consulting the manufacturer of the CMS, he said that it could be a resource problem of the web server.

Further research revealed that this could be a bug in PHP 8.1. A change to PHP 8.0 solved the problem.