Class Piwik\Plugins\Login\Auth contains 4 abstract methods and must therefore be declared abstract or implement the remaining methods (Piwik\Auth::getLogin, Piwik\Auth::getTokenAuthSecret, Piwik\Auth::setPassword, …)
in
/home/sites/plugins/Login/Auth.php line 250
Reload of page did not help
Restart of Apache server did not help
I experienced the same problem when I tried upgrading from 2.6.1 to 2.8.0 last night.
Fatal error: Class Piwik\Plugins\Login\Auth contains 4 abstract methods and must therefore be declared abstract or implement the remaining methods (Piwik\Auth::getLogin, Piwik\Auth::getTokenAuthSecret, Piwik\Auth::setPassword, …) in /mysite/piwik/plugins/Login/Auth.php on line 250
Fatal error: Class ‘Piwik_Plugin’ not found in /mysite/piwik/plugins/ExampleUI/ExampleUI.php on line 27
Any method for fixing this?
Many thanks.
I got the same error, when i updated to version 2.8.0.
I have just managed to fix my installation.
I downloaded the 2.8.0 files and uploaded them with Filezilla in Binary mode overwriting the existing files. I made a back-up of my database and piwik folder before doing so.
when I went to mywebsite.com - This website is for sale! - mywebsite Resources and Information. it then asks if I wanted to update my install and that my database is out of date and needs to be updated too.
There was still a complaint by the file integrity check that some piwik files were incorrect, but running update was successful and I have access to all my data again. I’ve only just got it back up and running, so need to carry out further checks, but hope this method works for others.
(tu)
This class was changed in 2.8.0, if you get this error that means that the files of the new version were not all correctly copied.
If you upload manually the 2.8.0 piwik files to the server (please take care not to ovewrite your config files) that should fix it.
Thanks for the report!
We tried improve the algorithm to copy the files to try fix this error. It’s a complete hit in the dark as we can only guess what problem could occur. Please upgrade to latest beta to enjoy latest fixes: I would like to test early beta and RC releases, how do I enable automatic updates to use these development versions? - Analytics Platform - Matomo
Really? You suggest to use beta versions on a production site?
yes it’s fine most of the time with our betas, but especially this one works well (already deployed on the http://demo.piwik.org )
Yes, but the last stable version is fine most time, also 
After manual upload, everything works fine again.
I have two installations of PIWIK on the same server under different domains. The first update works without any problems and the update at the 2nd installation create this error I reported above.