LCDUNG.

function read($id)
{
$sql = "select * from `tb_session` where `session_id`=$id";
mysql_query($sql);
//....
}

function write($id, $sess_data)
{
$sql = "INSERT INTO `tb_session` (`session_id`, `updated_on`) VALUES ('{$this->session_id}', NOW())";
mysql_query($sql);

}

function destroy($id)
{
$sql = "Delete from `tb_session` where `session_id`=$id";
mysql_query($sql);
}