Login form _validate hook
function openid_login_validate($form, &$form_state) {
$return_to = $form_state['values']['openid.return_to'];
if (empty($return_to)) {
$return_to = url('', array(
'absolute' => TRUE,
));
}
openid_begin($form_state['values']['openid_identifier'], $return_to, $form_state['values']);
}