PDO is disabled by default, and was even on default installs of 5.6 last I checked.
So while PDO may not be installed by a plain `apt-get install php5` or similar, I doubt the now deprecated `mysql` extension is installed by "default" in those scenarios either.
Edit: this approach also means that the PDO extension in php.ini will be commented, because its loaded by a package specific ini file e.g. /etc/php/7.0/fpm/conf.d/* which are generally symlinks to /etc/php/7.0/mods-available/
Just checked, seems enabled by default on FreeBSD.
(Commented out in php.ini doesn't mean disabled — here it's enabled in separate files like /usr/local/etc/php/ext-30-pdo_mysql.ini)
MODX Revolution uses PDO exclusively, never had problems with it on any hosting service.
Commented out in php.ini does mean disabled - as in not enabled. PDO isn't enabled by default in FreeBSD you still need to install a separate package for PDO.
> Commented out in php.ini does mean disabled - as in not enabled.
Not necessarily, as I explained here: https://news.ycombinator.com/item?id=13761550