Symptoms

• Roundcube Webmail failed to open with 500 error in browser.

• The following error appears  in /var/log/plesk-roundcube/errors :

  PHP Fatal error: Class 'PDO' not found in /usr/share/psa-roundcube/program/lib/Roundcube/rcube_db_mysql.php on line 144
  

• Listing of system php modules ( #php -m ) does not show pdo_sqlite module:

  # php -m | grep -i pdo 
  
  #
  

Cause

System PHP misconfiguration

Resolution

1. Comment the following directive in the /etc/psa-webmail/roundcube/php.ini file:

   #grep extension /etc/psa-webmail/roundcube/php.ini
   ;extension_dir = "./"
   

2. Turn on the pdo, pdo_mysql and pdo_sqlite extensions under Home > Tools & Settings > PHP Settings > %php_version% by OS vendor FastCGI application

3. Make sure that modules were activated using the following command:
   

   # php -m | grep -i pdo
   PDO
   pdo_mysql
   pdo_sqlite