We have been facing the error message "Fatal error: Class 'PDO' not found in includes/database/database.inc on line 184" in one of our Drupal sites. Googling up the error text had brought out a number of solutions which did not help to resolve the error in our case as there is no single cause of the error. However we managed to solve it using a different method. If you are facing the same scenario in your Drupal site and want to know how to solve fatal error with Class 'PDO' in Drupal sites the continue reading for the solution.