this error occur after upgrade from drupal 7 to drupal 9

Fatal error: Declaration of Drupal\Core\Database\Statement::fetchAll(int $mode = Drupal\Core\Database\PDO::FETCH_BOTH, $column_index = null, $constructor_arguments = null) must be compatible with PDOStatement::fetchAll(int $mode = PDO::FETCH_DEFAULT, mixed ...$args) in C:\xampp\htdocs\dar-drupal9\core\lib\Drupal\Core\Database\Statement.php on line 169<?php