In the Administrative Overview section of NextCloud, the following warning appeared:

The PHP OPcache module is not properly configured. See the documentation ↗ for more information. The OPcache interned strings buffer is nearly full. To assure that repeating strings can be effectively cached, it is recommended to apply opcache.interned_strings_buffer to your PHP configuration with a value higher than 8.

Edit PHP.ini with Vim to adjust opcache.interned_strings_buffer and opcache.memory_consumption. E.g. Just increase their values for now, as follows:

Find and edit the php.ini file in the following directory:

cd /etc/php/8.1/apache2

ls

[to list php.ini file]

Use Vim to edit the php.ini file.

sudo vim php.ini

Change the value of the buffer from 8 to 16 Change the value of memory consumption from 128 to 256 By editing the following settings with php.ini

opcache.interned_strings_buffer=16
opcache.memory_consumption=256

Save and exit vim.

Restart the Apache2 service

sudo systemctl restart apache2

See if the warning message disappeared from the nextcloud administration overview.