How to Update an old theme for the latest wordpress version

Question

Ok, so to start off I'm no Theme developer, but I have a little bit of experience with PHP, and quite a bit of experience (Several Years constant work) with wordpress in general.

I have a current client that wants to use a wordpress theme he saw exampled on another website. I found out that it's the (now outdated) Ridizain theme, which hasn't been updated in a few years. I know the theme is a modification of the Twenty Fourteen theme, so I could probably make some CSS Changes to 2014 and come up with the same look.

However, I'm wondering If I could just download the Ridizain theme and make any necessary changes to update it for the latest version of wordpress. I have a test server that I run and it does not seem to have any direct conflicts when I install it.

Is there a resource out there for Theme developers that details what needs to be changed/updated in a theme to bring it in line with each new version of wordpress? If not, where would I begin looking for what needs to be changed/watched out for?

Thanks!

Answer 1

WordPress is exceptionally backwards compatible, so it is typical even for older themes to just work for a long time.

However for solid results you would want to perform several meaningful actions:

1. Straight up code review, if your experience and time allows. Just read through all of the code, gauge if it makes sense.

2. Running through everything with WP_DEBUG enabled. Straight errors will come up, but also any formally deprecated functions/features will emit warnings with suggestions to update.

3. Run through Theme Check plugin and see what comes up. You don't necessarily want to bother with all of that for custom theme, but it's a good to see what's up.

4. If you customize theme for private use — make a proper fork of it, changing name and details. Otherwise you risk invalid update from the repo destroying your changes. However do keep proper attribution to original author for copyright/licensing reasons.