title: Error: Undefined class constant 'MYSQL_ATTR_USE_BUFFERED_QUERY'
body: <p>Currently I'm getting this kind of message and I don't know how to fix it.</p>
  
  <p>The command <code>php -m</code> tells me that PDO and pdo_mysql are there.</p>
  
  <p>I'm using Drupal-8 with php7.1.20 on Ubuntu 18.04.1 LTS</p>
  
  <blockquote>
    <p>[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}</p>
  </blockquote>