So I maintain a open source PHP app that wraps youtube-dl, providing an UI for it basically. Some guy on a forum DMd me saying it's not working for him. I asked him what php version he used and if the file permissions are correct (the script makes and switches directories, so the permissions can't be root but need to be www-data).

He answers with PHP 7.2 (the newest that's rare) and says the file permissions are correct.

After 2 weeks the problem still persists and ofc I am doubting my code here. We finally get online together and I can use anydesk to work on his machine.

I discovered 2 things.

1) File permissions were just completely wrong.

2) PHP WASN'T EVEN INSTALLED

So what did I learn?

Never trust the user and I am glad that I work as a dev, not as a tech support.