会话变量：在插入后从 sql 字段保存自动增量

Question

I want to save in a session variable on php an auto increment value field from one SQL table, just next to do the insert on that table. Why it appears empty? What should I do?

Because I check my sql statement on the database and everything is correct, all of that and have values.

$usersetdataregister="INSERT INTO `questionnaire`.`tbluserset`(`UserIDFKPK`, `QuestionSetIDFKPK`) VALUES ('$UserId','0')"; 

mysql_query($usersetdataregister);

$query_usersetID= "SELECT tbluserset.UserSetIDPK 
                   FROM tbluserset 
                   INNER JOIN (SELECT US.UserIDFKPK, MAX(US.Timestamp) AS MaxTimestamp
                               FROM tbluserset AS US
                               WHERE US.UserIDFKPK ='$UserId' 
                               GROUP BY US.UserIDFKPK) AS USL ON tbluserset.UserIDFKPK = USL.UserIDFKPK AND tbluserset.Timestamp = USL.MaxTimestamp";

 $row_UserSetIDPK = mysql_query($query_usersetID);

 $UserSetID= $row_UserSetIDPK['UserSetIDPK'];
 $_SESSION['UserSetIDPK']= $UserSetID;  

Next to do this i want use the value on a query statement and UserSetIDPK appears empty.

Answer 1

I think you forgot to start your session.

session_start();
$_SESSIONS['UserSetIDPK'] = $UserSetID;

You should also check what $row_UserSetIDPK is returning. If it's empty then there is something wrong with your query, or he can't find any results in your database.

If it's not empty, you should see if $row_UserSetIDPK['UserSetIDPK'] is the right way to get your value. to debug try this:

var_dump($row_UserSetIDPK);die();

Hope this helps a bit, 'cause your post is quite a mess! :-)