Switch theme via URL - doesn't switch until next page load for logged in users only.

This worked fine with anon users.

After much frustration, it seems something happens when user_save() is called so that changing $user->theme doesn't immediately change the displayed theme. I moved $user->theme = $form_values['theme']; out of the if statement and put it BEFORE user_save() and it worked.

I'm still a little confused as to why, but this change fixed our problem... I'll let another investigate further.

I changed the following code

function switchtheme_switch_form_submit($form_id, $form_values) {
  global $user;

  if ($user->uid > 0) {
    // Save the setting in the db for logged in users.
    // We do not validate the input here, because that is done in init_theme()
    // already.
    if (user_save($user, array('theme' => $form_values['theme']))) {
      $user->theme = $form_values['theme'];
    }
    $_SESSION['custom_theme'] = $form_values['theme'];
  }
  elseif (user_access('switch theme')) {
    // Save the setting in the session for anonymous users.
    $_SESSION['custom_theme'] = $form_values['theme'];
  }
}

TO:

function switchtheme_switch_form_submit($form_id, $form_values) {
  global $user;

  if ($user->uid > 0) {
    // Save the setting in the db for logged in users.
    // We do not validate the input here, because that is done in init_theme()
    // already.
    $user->theme = $form_values['theme'];
    user_save($user, array('theme' => $form_values['theme'])); 
    $_SESSION['custom_theme'] = $form_values['theme'];
  }
  elseif (user_access('switch theme')) {
    // Save the setting in the session for anonymous users.
    $_SESSION['custom_theme'] = $form_values['theme'];
  }
}