如果要计算行数，可以使用PDO做到这一点:

If you want to count the rows you can do this with PDO:

$sql = 'select * from users';
$data = $conn->query($sql);
$rows = $data->fetchAll();
$num_rows = count($rows);

在PDO中使用SELECT语句时，无法直接对行进行计数.

There is no way to directly count rows when using a SELECT statement with PDO.