PHP Session Handling (read function) Problem

I have a class that handle SESSION in my code and store session data in DB. In Read callback function I write a query and load data from DB and return the value but when dump $_SESSION this is empty!

I trace the code and my query is corrent and data load but not set session value. this problem apear in subdomains but session_id and COOKIE is correct.

my read function code:

function read($session_id)
{              
    $result = @mysql_query("
        SELECT
            session_data
        FROM
            session_table
        WHERE
            session_id = '".$session_id."' AND
            session_expire > '".time()."'
    ");

    if (is_resource($result) && @mysql_num_rows($result) > 0) {
        $fields = @mysql_fetch_assoc($result);
        return $fields["session_data"];
    }


        return "";

    }

My Log:

read function log: 
            SELECT
                session_data
            FROM
                sessions_table
            WHERE
                session_id = '389dd7fc7bc19ffead7274c0ad860896' AND
                session_expire > '1295954400'
read function result log:
Array
(
    [session_data] => corret serialized data
)

write function log:
                UPDATE
                    sessions_table
                SET
                    session_data = '开发者_StackOverflow社区',
                    session_expire = '1295955840'
                WHERE
                    session_id = '389dd7fc7bc19ffead7274c0ad860896'

Don't use the error supression operator (@). That's what prevents you from seeing the errors you made in your code. That's why you don't know where the error is in your code. That's why you have to ask where the error is in your code.

Actually, I do not see any errors in your code either, but e.g. if the database was not set up up correctly or there were an error in your SQL syntax, mysql_query would tell you that.