If you saw this error in the browser during WordPress installation:
Your PHP installation appears to be missing the MySQL extension which is required by WordPress.
That's because WordPress requires MySQL extension of PHP to access the database.
In this moment, you need to install php-mysqlnd module.
[root@web ~]# yum -y install php-mysqlnd
For Debian distros, you can use apt-get to install this module.
No worry about the abstraction layer of database connection, the dependency module php-pdo will be installed as well.