PDO MySQL returns php value type "string" for column type "YEAR"

Description

The following code:

<?php
/**
 * Given:
 * CREATE TABLE `t` (
 *   `y` year(4) DEFAULT NULL,
 *   `m` tinyint(3) DEFAULT NULL
 * ) ENGINE=InnoDB DEFAULT CHARSET=utf8
 * INSERT INTO t VALUES (2001, 11);
 */
$pdo = new PDO($dsn, null, null, [ PDO::ATTR_EMULATE_PREPARES => false ]);
var_dump($pdo->query("SELECT * FROM t")->fetchAll(PDO::FETCH_ASSOC));

Resulted in this output:

array(1) {
  [0]=>
  array(2) {
    ["y"]=>
    string(4) "2001"
    ["m"]=>
    int(11)
  }
}

But I expected this output instead:

array(1) {
  [0]=>
  array(2) {
    ["y"]=>
    int(2001)
    ["m"]=>
    int(11)
  }
}

This breaking change occurs between PHP v8.0 & v8.1.

PHP Version

8.1.6

Operating System

Alpine 10.2

Start with the PDO MySQL reproducer in the issue and compare its result on PHP 8.0 and 8.1, focusing on the YEAR column returned by FETCH_ASSOC. Determine whether the observed type change is expected and identify the relevant PHP documentation entry; done means the behavior and any required documentation change are confirmed.