php中如何查询指定时间段的数据？

$timea = strtotime($_POST['timea']);
$timeb = strtotime($_POST['timeb']);
$sq2="select * from `ecs_order_info` 
where add_time between '$timea' and '$timeb' and `quanxian`='$dangqian' 
order by `order_id` DESC limit 50";
$sql = mysql_query($sq2);

date('Y-m-d H:i:s', 1156219870);

strtotime('2010-03-24 08:15:42');

select FROM_UNIXTIME(1156219870);

Select UNIX_TIMESTAMP('2006-11-04 12:23:00′);

$sql=”select * from message Where DATE_FORMAT(FROM_UNIXTIME(chattime),'%Y-%m-%d') = DATE_FORMAT(NOW(),'%Y-%m-%d') 
order by id desc”。