Fixing nginx Error: Undefined constant PDO::MYSQL_ATTR_USE_BUFFERED_QUERY I install a lot of Drupal sites day to day, especially when I'm doing dev work. In the course of doing that, sometimes I'll be working on infrastructure—whether that's an Ansible playbook to configure a Docker container, or testing something on a fresh server or VM. In any case, I run into the following error every so often in my Nginx error.log: "php-fpm" nginx Error: Undefined constant PDO::MYSQL_ATTR_USE_BUFFERED_QUERY ...