Unable to open Roundcube Webmail with error 500: Class 'PDO' not found

Symptoms

• Roundcube Webmail failed to open with 500 error in the 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 does not show pdo_sqlite module:

  # php -m | grep -i pdo 

• There is a custom value for extension_dir directive:

  # php -i | grep extension_dir
  extension_dir => ./ => ./

Cause

System PHP misconfiguration.

Resolution

Note: This article may require additional administrative knowledge to apply. If any help required, contact the server’s administrator or hosting support.

1. Log in to Plesk server via SSH

2. Comment out extension_dir directive in the /etc/psa-webmail/roundcube/php.ini and /etc/php.ini files, e.g.:

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

   So, the value for extension_dir directive should look as follows:

   # php -i | grep extension_dir
   extension_dir => /usr/lib64/php/modules => /usr/lib64/php/modules

3. Log into Plesk.

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

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

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