I see absolutely no reason to do this. There is no difference between
MySQL and MariaDB in terms of PDO. Sure, the actual RDBMSs have
differences, but they play no role when it comes to PDO.
If MariaDB decides to change the protocol some day then we would need
a new driver to replace mysqlnd. Only then it would make sense to have
PDO_mariadb extension. But that is unlikely to happen any time soon.
The purpose of PDO subclasses is to offer driver specific
functionality and differentiate SQL syntax flavours. MariaDB and MySQL
use the same driver so they offer the same functionality and they use
the same SQL syntax (at least the parts that matter). And we must
remember that MariaDB is not the only MySQL-like DB out there. We are
not going to create a name alias for every possible fork of MySQL that
ever exists. It would be pointless.
