问PHP当在包装器中调用数据库时如何获取上次插入的is

EN

<?php
$sql = "insert into user (firstname, lastname) values (:firstname, :lastname)";
$arg = array("John", "Doe");
$stmt = pdo($sql, $arg);

$id = $pdo->lastInsertId();
print $id;


function pdo($sql, $args = NULL){

  $dsn = "mysql:host=localhost;dbname=db;charset=utf8mb4";

  try {
    $pdo = new \PDO($dsn, "user", "123");
  } catch (\PDOException $e) {
    throw new \PDOException($e->getMessage(), (int)$e->getCode());
  }

  if (!$args){
    return $pdo->query($sql);
  }

  $stmt = $pdo->prepare($sql);
  $stmt->execute($args);

  return $stmt;

}

?>