after upgrading to PHP 8.0.25 I get the following error:
Uncaught TypeError: Cannot access offset of type string on string in D:\laragon\www\lindenschule\wp-includes\media.php:779
After deactivating GP Premium, the fatal error no longer appears.
I have additionally migrated the website to my local development environment (laragon), enabled debug and additionally also installed and enabled the Query Monitor plugin. Even there I get the above error.
More information is available in private information.
Extremely curious: I just noticed that in the menu item “Posts” were initially displayed to me only the first 4 posts. I then deleted the following posts to the trash. After I restored the posts, the website was basically displayed correctly. However, when I go to the trash, the following message appears: “There was a critical error on your website. Please check your site administrator email inbox for further instructions.” There is obviously a post there, but it is not displayed.
After that, I clicked on the “Empty Trash” button and now the website seems to be ok.
BTW: I had a repair of the database via define('WP_ALLOW_REPAIR', true);
already done before. Without success.
Amazing that the problem was not obvious with PHP 7.4.x.