yii\db\Connection::getIsActive PHP Method

    public function getIsActive()
    {
        return $this->pdo !== null;
    }

 /**
  * Extend internal resources array
  *
  * @param string $resourceName
  * @param Connection $connection
  * @param string $className
  * @param boolean $connect
  */
 public function extendResourceArray($resourceName, $connection, $className, $connect = false)
 {
     $this->resources['Resources'][$resourceName]['Connection'] = $connection;
     $this->resources['Resources'][$resourceName]['Connected'] = $connection->getIsActive();
     $this->resources['Resources'][$resourceName]['Aliases'] = array();
     $this->resources['Resources'][$resourceName]['Settings'] = array('class' => $className, 'dsn' => $connection->dsn, 'username' => $connection->username, 'password' => $connection->password, 'attributes' => $connection->attributes, 'charset' => $connection->charset, 'enableSchemaCache' => $connection->enableSchemaCache, 'schemaCacheDuration' => $connection->schemaCacheDuration, 'schemaCacheExclude' => $connection->schemaCacheExclude, 'schemaCache' => $connection->schemaCache, 'enableQueryCache' => $connection->enableQueryCache, 'queryCacheDuration' => $connection->queryCacheDuration, 'queryCache' => $connection->queryCache, 'emulatePrepare' => $connection->emulatePrepare, 'tablePrefix' => $connection->tablePrefix, 'connect' => $connect);
 }