Panel not working on Production Server

Hey Kirby Community!

I’ve run into a weird issue the other day. I have an early K3 installation on a production server (shared hosting, worked liked a charm for I don’t know 6 months or so) where the client did some updates last Friday. (Unfortunately I don’t know what kind of updates — and the client can’t remember either, he just reached out and said “the panel ist not working anymore”).

When opening the /panel URL I get the following error message:
The panel assets cannot be installed properly. Please check permissions of your media folder.

So I tried a couple of things to get it running again (unfortunately nothing worked):

  • Updating Kirby to the latest version
  • Checked and updated PHP versions (to the latest 7.3 that’s available on that server)
  • Found an old thread where someone found out it’s caused by a missing composer.json file and added that file (while it’s being added when updating to the latest K3 version anyway and it should be fixed according to an issue on GitHub)
  • Checked folder permissions (even set it to 777).
  • Deleted the media folder (as I read somewhere it gets regenerated)
  • Tracked down the error line inside /kirby/src/cms/panel.php and commented it out (and set debug: true) so it resulted in the following error:
Call to undefined function Kirby\Data\json_decode()

in /kirby/src/Data/Json.php on line 37

Does anyone have any ideas on what else I could try?

Could you please post your PHP info? json_decode() is a PHP function, it should usually be available.