Corrupt localconfig.php

[Triskal]

I have run into this problem:
viewtopic.php?f=6&t=3046
https://github.com/contao/core/issues/2616

Some one in the thread on this forum suggested that updating Contao to 2.10 or later would fix the problem. For me it doesn't. I do not know enough german to understand what the problem is from the github thread. The broken installation is 2.10.4

What are the most common things that cause this problem?

[Medianomaly]

If you open your localconfig.php, what do you see? Does anything look broken or invalid, or does it look like the example in the other thread you linked to (where all the options missing)?

Can you use your site at all -- log into the back-end or get to the install tool?

You can maybe try backing up and deleting localconfig.php completely, then log into the install tool. The tool might recreate the file from scratch for you. Although you'll lose your custom settings if you do this.