Ubuntu – adminer- None of the supported PHP extensions (MySQLi, MySQL, PDO_MySQL) are available

What version of Ubuntu? Are you sure you need to add those lines to php.ini?

I have versions 10.03 and 11.10, and both are similar in that none of that is in php.ini, but is in the directory under that one, called conf.d.

In conf.d/mysql.ini, I have:

extension=mysql.so

In conf.d/pdo.ini, I have:

extension=pdo.so

In conf.d/pdo_mysql.ini, I have:

extension=pdo_mysql.so

I don't have the newest version, and I also don't use any special LAMP stack, just the standard apps I installed separately, if that makes any difference. But I never had any problems, and never had to explicitly install PDO that I can remember.

At this stage I would simply recommend "turning it off and on again" by doing:

sudo apt-get purge php-common php5-common

followed by

sudo rm -r /etc/php

And then reinstalling PHP 7.0 and mysql modules:

sudo apt-get install libapache2-mod-php php-mysql

You may also try just purging and reinstalling mysql modules, first removing the package:

sudo apt-get purge php7.0-mysql

And the installing them again:

sudo apt-get install php-mysql

In both cases it's important to use apt-get purge instead of apt-get remove to delete any existing configuration files and package states.

The least destructive way would be trying to re-enable mysql modules using phpenmod command:

sudo phpenmod mysqlnd pdo_mysql

It's hard to give you correct advice if we don't know what mayhem you created on your system.