Clarification about PHP mysql configuration

Hey there,

according to admin manual, the following php mysql module configuration could be used: https://docs.nextcloud.com/server/12/admin_manual/configuration_database/linux_database_configuration.html#configuring-a-mysql-or-mariadb-database

# configuration for PHP MySQL module
extension=pdo_mysql.so

[mysql]
mysql.allow_local_infile=On
mysql.allow_persistent=On
mysql.cache_size=2000
mysql.max_persistent=-1
mysql.max_links=-1
mysql.default_port=
mysql.default_socket=/var/lib/mysql/mysql.sock  # Debian squeeze: /var/run/mysqld/mysqld.sock
mysql.default_host=
mysql.default_user=
mysql.default_password=
mysql.connect_timeout=60
mysql.trace_mode=Off

Is this something like a recommendation or an example to just show the available settings?
As can be seen, some values are empty, others have just the default value (http://php.net/manual/en/mysql.configuration.php) and explicitly the manual just gives the advice to ensure that mysql.default_socket points to the right socket location. This makes sense, although it is handled and usually set right within default php.ini.

Besides, I am not sure, that at least since PHP7.0 these config values change anything about the pdo_mysql extension used by Nextcloud. This has it’s own settings: http://php.net/manual/en/ref.pdo-mysql.php#pdo-mysql.configuration
pdo_mysql further depends on mysqlnd with again brings its own settings: http://php.net/manual/en/mysqlnd.config.php
So I am a bid confused if the mysql.<...> settings do have any influence. They also do not show up on phpinfo().