core/Settings/Storage/Backend/BaseSettingsTable.php

<?php

/**
 * Matomo - free/libre analytics platform
 *
 * @link    https://matomo.org
 * @license https://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
 */

namespace Piwik\Settings\Storage\Backend;

use Piwik\Concurrency\Lock;
use Piwik\Container\StaticContainer;
use Piwik\Db;

abstract class BaseSettingsTable implements BackendInterface
{
    /**
     * @var Db\AdapterInterface
     */
    protected $db;

    /** @var Lock */
    protected $lock;

    public function __construct()
    {
        $this->lock = StaticContainer::getContainer()->make(
            Lock::class,
            array ('namespace' => 'PluginSettingsTable')
        );
    }

    protected function initDbIfNeeded()
    {
        if (!isset($this->db)) {
            // we do not want to create a db connection on backend creation
            $this->db = Db::get();
        }
    }
}