Internal Server Error after swiching PHP version

Nextcloud version: 17.0.2
Operating system and version: Hosted webservice (netcup), Linux af995 4.9.0-0.bpo.9-amd64 #1 SMP Debian 4.9.168-1+deb9u5~deb8u1
Apache or nginx version: Apache
PHP version: 7.3.13

The issue you are facing:

When accessing the web instance I only get one error message on an otherwise white page:

Internal Server Error

The server encountered an internal error and was unable to complete your request.
Please contact the server administrator if this error reappears multiple times, please include the technical details below in your report.
More details can be found in the server log.

(There are no “technical details below”, just a white page.)

Is this the first time you’ve seen this error? (Y/N): Y

Steps to replicate it:

Just before that error appeared, I switched the PHP version from 7.2 to 7.4 in the admin backend of my web hosting provider. Then I got an error message that PHP 7.4 is not supported. Then I switched PHP back to 7.3 and the above mentioned error message appeared. I also trieded PHP 7.2 (no change, still the error).

The output of your Nextcloud log in Admin > Logging:

(I cannot access that page)

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

bash-4.3$ cat config.php 
$CONFIG = array (
  'instanceid' => '',
  'passwordsalt' => '',
  'secret' => '',
  'trusted_domains' => 
  array (
    0 => 'www.mydomain.tld',
    1 => 'mydomain.tld',
  'datadirectory' => '',
  'overwrite.cli.url' => '',
  'dbtype' => 'mysql',
  'version' => '',
  'dbname' => '',
  'dbhost' => '',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => '',
  'dbpassword' => '',
  'installed' => true,
  'mail_from_address' => 'admin',
  'mail_smtpmode' => 'smtp',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_domain' => '',
  'maintenance' => false,
  'theme' => '',
  'loglevel' => 2,
  '' => 'stable',
  'mail_smtpsecure' => 'tls',
  'mail_smtphost' => '',

The output of your Apache/nginx/system log in /var/log/____:
(these files are massive, I could paste parts of them, what should I look for?)

Access the nextcloud.log file from the command line. You should find it in the Nextcloud data directory by default. Additionally have a lock on your web server log file. I would assume that most likely missing php modules are reported. The search function of this forum should show you many matches concerning this kind of problem - give it a try :wink:

Thanks! Yes, I find two log files, which are very large (24 MB and 121 MB).

 24M Dec 28 18:13 nextcloud.log
121M May  7  2019 nextcloud.log.1

looking at the nextcloud.log file I find no good information.

Still browsing…

Edit: I fiddled around with my PHP settings. Changing a open_basedir setting helped. This is probably something that has been resetted by changing the PHP version.