function LoadClass()
{
$db = new DB_Connect();
$major_id = (string) $_POST['major_id'];
$statement = 'select * from class where state = 1 and major_id=:major_id';
$result = $db->prepare($statement);
$result->execute(array(':major_id' => $major_id));
$index = 0;
$ret = "";
while ($row = $result->fetch()) {
$element = new classes();
$element->setVal($row['class_id'], $row['class_name']);
$ret[$index++] = $element;
}
echo json_encode($ret);
}