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How To Make Old WordPress Themes Compatible With New Versions

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So you want to make your old WordPress themes compatible with newer versions of WordPress. With WordPress 3.0 right around the corner, theme compatibility is something on a lot of people’s minds. It’s pretty simple: do absolutely nothing.

I’ve been making WordPress themes since around WordPress 2.3 was released, and guess what? Those themes still work today and there’s nothing I need to do to keep them working with newer versions of WordPress.

  • Will they have threaded comment functionality (circa 2.7)? Nope, they probably still have “single level” comments though.
  • Will it use post_thumbnails to handle post thumbnails (circa 2.9)? Nope, but not every theme makes use of post thumbnails anyway.
  • Will they have the new navigation menus, custom header and background images introduced in the upcoming WordPress 3.0? Nope, and keep in mind not every theme will have a need for custom background or header images.

Most of these features I would consider optional. With maybe the exception of threaded comments or the new menu system, a lot of themes won’t even need or be designed around things like custom post thumbnails or header images.

So please, stop worrying about if your theme is going to break when you upgrade WordPress. No offense to my plugin developer friends, but 99% of the time WordPress breaks with a core upgrade, it’s a plugin’s fault (and it probably had it coming due to suspect plugin coding practices).

If a theme has a custom function that conflicts with a new WordPress function, the same thing could happen to themes too, so it is possible. This is probably the only “bug” I’ve ever heard of happen with a new core upgrade (and not every theme used the get_categories function).

To be honest, I’ve never seen a theme completely break, and I probably never will. I’d be interested to hear your thoughts in the comments, what do you think about making themes “compatible” with new versions? Have you ever seen a theme break because of a new WordPress version?

If you want your WordPress theme to take advantage of the new features that will be available once WordPress 3.0 is released, this article has some good info on integrating custom backgrounds, headers, menus, among other things.

  • http://matt-bridges.com Matt Bridges

    I really think that the issue with theme development is making a theme compatible with OLD versions of WordPress. You may see, in plugins especially, function checks to see if the wanted function exists or uses a work-around otherwise. I have never seen a theme break or heard of a theme breaking after a new WordPress version release.

    Good article. Definitely worth a thought!

    • Leland

      Hey Matt, really good point.

      If a theme has a feature like post_thumbnails, and doesn’t use a function_exists check, it will cause a fatal error in anything before 2.9.

      I guess we can hope that users keep their WordPress installations up-to-date.

  • http://themetoday.com Beau

    No need to fix it if ain’t broken!

  • http://www.kevinkossowan.com/ Kevin

    I upgraded to 3.0 and it won’t title my blog properly anymore. Not only will it not show the previous image it used to, it won’t even read the blog title – it simply is titled ‘liteword’ – the theme’s name. So to me, this upgrade seriously screwed up the theme I use!! Any idea how to get around this issue?

  • Danielle

    I’m working on a site, and the guy who own’s the server where the site is located upgraded to 3.0 just yesterday….. Now, the “top ads” part of the blog isn’t showing – Its the Beauty Magazine theme.

    It has a Buy Cialis link at the top that I can’t get off (but that was on there at least a week prior). The error in the theme didn’t occur until the upgrade…..hhmmmm….

    • Leland

      Danielle, it sounds like your WordPress site was hacked which seems to be a much more serious issue than the “top ads” part not showing up.

      If that’s a widget area, you may just have to reload the widgets.

  • http://linkedbees.com Donald McIntyre

    Leland, I disagree completely. As a user of the GuruQ Theme since the 3.0 version of WP it doesn´t break, but it doesn´t work either. When visitors ask a question it takes them to a “page not found” So at least this theme was fundamentally turned useless.

    Best, Donald.

    PS: I came here because of the title, is there a way of making an old theme work with the new WP versions?