Themes usually will have to be updated when a new version of Geeklog comes out, as new functionality will often require new template files or changes in existing files.
These theme changes are always documented, so you should always consult the Geeklog documentation first.
When upgrading a theme or developing a new theme, you may end up in a situation where your site simply won't work any more, as a theme file could not be loaded or it's not working properly any more. In those cases, it's always recommended to have a second theme around that's known to be working, e.g. the Professional theme that ships with Geeklog.
To get your site back into a working state, do this:
- Rename the directory of the faulty theme. The new name doesn't matter, it just has to be different from the name that it had so far.
- In Geeklog's siteconfig.php, set the default theme back to the working theme, e.g.
$_CONF['theme'] = 'professional';
Now you can get back into your site. Go go to the Configuration admin panel and change the default theme back to a working one, then remove the above line from siteconfig.php again.
Tip: When Geeklog can't find the current theme (i.e. the one that the current user has selected in their preferences and which is also stored in a cookie on the user's browser), it will fall back to the default theme. So when trying out new themes, you should change the theme in your account settings first (to see if it works) before switching over the entire site (i.e. changing the default theme in the Configuration). That way, you can simply rename (or delete) faulty themes and still have a working fallback without having to edit siteconfig.php every time.