Sers! Once again, I tried to install some software. It requires PHP>=7.3, so I decided I'd follow a tutorial to add additional PHP versions. I chose PHP8.0, this is the tutorial: https://beyond.lol/ispconfig-mehrere-php-versionen-mit-apt-installieren-auf-ubuntu-18/ (Achtung, Krautspeak!) When PHP was default 8.0, ISPConfig was kinda "empty" (apart from header) after login, so I set default PHP back to 7.2 and it worked again. Checking "PHP -v" did display PHP8.0 when it was running, though. It displays 7.2 again after changing defaults. Now, in ISPConfig when I set a page to PHP8.0, it throws an Internal Error at me. Code: Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator at [email protected] to inform them of the time this error occurred, and the actions you performed just before this error. More information about this error may be available in the server error log. Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request. This... doesn't help me much so I checked the apache2/error.log, which says a lot, including: Code: PHP Warning: PHP Startup: Unable to load dynamic library 'pdo_mysql' (tried: /usr/lib/php/20170718/pdo_mysql (/usr/lib/php/20170718/pdo_mysql: cannot open shared object file: No such file or directory), /usr/lib/php/20170718/pdo_mysql.so (/usr/lib/php/20170718/pdo_mysql.so: undefined symbol: mysqlnd_allocator)) in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library 'imagick.so' (tried: /usr/lib/php/20170718/imagick.so (/usr/lib/php/20170718/imagick.so: undefined symbol: zend_string_init_interned), /usr/lib/php/20170718/imagick.so.so (/usr/lib/php/20170718/imagick.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library 'memcache.so' (tried: /usr/lib/php/20170718/memcache.so (/usr/lib/php/20170718/memcache.so: undefined symbol: zend_string_init_interned), /usr/lib/php/20170718/memcache.so.so (/usr/lib/php/20170718/imagick.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0 - What is " in Unknown at line 0" supposed to mean? Why is it an undefined symbol? How to define it? - Is there anything I have to setup in a php.ini file or somewhere? - There is a memcache.so and a imagick.so in /usr/lib/php/2021moredatedigits/ - so why is it targeting the older - There already is a pdo_mysql.so in /20170718/ - but it seems looking for a file without ".so"? "service PHP8.0-fpm status" shows running, no issues listed.