How To Make Old WordPress Themes Compatible With New Versions

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.

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