Description:
------------
Values returned by PDO for MIN/MAX query are wrong compared to actual mysql output. Either a bug in PDO or the MySQL libraries used by PDO?

Test script:
---------------
$pdo = new PDO($dsn, $user, $pass);
$pdo->query('drop table test');
$pdo->query('create table test (i int not null auto_increment, ts bigint(20), primary key (i))');
$pdo->query('insert into test (ts) value (3600000),(10800000),(14400000)');

$sql = '
SELECT
	MIN(agg.prev_ts),
	MAX(agg.prev_ts),
	LEAST(MIN(agg.prev_ts),	MAX(agg.prev_ts)),
	MAX(agg.ts) - MIN(agg.prev_ts)
FROM (
	SELECT ts, @row:=@row+1 AS row,
		IF (@prev_ts != 0, @prev_ts, NULL) AS prev_ts,
		@prev_ts := ts
	FROM test
	CROSS JOIN (SELECT @prev_ts := 0, @row := 1) AS vars
	ORDER BY ts ASC
) AS agg
GROUP BY (row DIV 3)
ORDER BY ts ASC
';
foreach($pdo->query($sql, \PDO::FETCH_ASSOC) as $row) {
	if ($row['MIN(agg.prev_ts)']) print_r($row); // show 2nd row only
}

Expected result:
----------------
Array
(
    [MIN(agg.prev_ts)] => 3600000
    [MAX(agg.prev_ts)] => 10800000
    [LEAST(MIN(agg.prev_ts),    MAX(agg.prev_ts))] => 3600000
    [MAX(agg.ts) - MIN(agg.prev_ts)] => 10800000
)

Actual result:
--------------
Array
(
    [MIN(agg.prev_ts)] => 10800000
    [MAX(agg.prev_ts)] => 3600000
    [LEAST(MIN(agg.prev_ts),    MAX(agg.prev_ts))] => 10800000
    [MAX(agg.ts) - MIN(agg.prev_ts)] => 3600000
)