Currently I'm getting this kind of message and I don't know how to fix it.
The command php -m tells me that PDO and pdo_mysql are there.
I'm using Drupal-8 with php7.1.20 on Ubuntu 18.04.1 LTS
[Tue Sep 04 09:27:48.210064 2018] [php7:notice] [pid 2183] [client 10.56.99.1:53758] Error: Undefined class constant 'MYSQL_ATTR_USE_BUFFERED_QUERY' in /var/www/dev/web/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php on line 134 #0 /var/www/dev/web/core/lib/Drupal/Core/Database/Database.php(376): Drupal\Core\Database\Driver\mysql\Connection::open(Array)\n#1 /var/www/dev/web/core/lib/Drupal/Core/Database/Database.php(166): Drupal\Core\Database\Database::openConnection('default', 'default')\n#2 [internal function]: Drupal\Core\Database\Database::getConnection('default')\n#3 /var/www/dev/web/core/lib/Drupal/Component/DependencyInjection/PhpArrayContainer.php(79): call_user_func_array('Drupal\\Core\\Dat...', Array)\n#4 /var/www/dev/web/core/lib/Drupal/Component/DependencyInjection/Container.php(171): Drupal\Component\DependencyInjection\PhpArrayContainer->createService(Array, 'database')\n#5 /var/www/dev/web/core/lib/Drupal/Component/DependencyInjection/PhpArrayContainer.php(260): Drupal\Component\DependencyInjection\Container->get('database', 1)\n#6 /var/www/dev/web/core/lib/Drupal/Component/DependencyInjection/PhpArrayContainer.php(62): Drupal\Component\DependencyInjection\PhpArrayContainer->resolveServicesAndParameters(Array)\n#7 /var/www/dev/web/core/lib/Drupal/Component/DependencyInjection/Container.php(171): Drupal\Component\DependencyInjection\PhpArrayContainer->createService(Array, 'cache.container')\n#8 /var/www/dev/web/core/lib/Drupal/Core/DrupalKernel.php(516): Drupal\Component\DependencyInjection\Container->get('cache.container')\n#9 /var/www/dev/web/core/lib/Drupal/Core/DrupalKernel.php(877): Drupal\Core\DrupalKernel->getCachedContainerDefinition()\n#10 /var/www/dev/web/core/lib/Drupal/Core/DrupalKernel.php(469): Drupal\Core\DrupalKernel->initializeContainer()\n#11 /var/www/dev/web/core/lib/Drupal/Core/DrupalKernel.php(665): Drupal\Core\DrupalKernel->boot()\n#12 /var/www/dev/web/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))\n#13 {main}
