Things you should check
First you should check phpinfo() for the pdo_drivers installed.
if u use IIS server , you should check php extensions installed or not.
check php.ini for extensions_dir is properly given
check you ext folder in php contains pdo_mysql dlls
Some times the problem may occur due to zend server installation .You should check zend server is properly using the php extensions
After that check simple php-mysql connection using the following functions
mysql_connect('localhost:3306','root','root');
mysql_select_db('testdrive');
If it works then go with Yii, Slim, Zend php-mysql connections