How enable pdo_mysql

Install pdo:

yum install php-devel php-pear mysql-devel httpd-devel
pecl install pdo
PHP_PDO_SHARED=1 pecl install pdo_mysql

Then edit the /etc/php.ini file with your favorite commandline texteditor (vi, vim, nano,...) (access the machine through ssh) and add these lines:

extension=pdo.so
extension=pdo_mysql.so

Restart the webserver and you should be all set. Cudos to http://karoshiethos.com/2008/07/24/installing-pdo_mysql-on-centos/