Exists
Exists is a simple function that returns TRUE or FALSE depending on whether the object has a corresponding database record. For example:
$id = 42;
// Get user
$u = new User();
$u->get_by_id($id);
// Check if we actually got a user back from the database
if ($u->exists())
{
// Yes, we did!
}
else
{
// No, we didn't!
}