Create a ‘Must Use’ Plugin for WordPress

Some of you are like me: “frequent theme changer guy”. Here’s a trick I’ve learned to keep from having to re-write code every time I get bored with a theme: I use the “Must Use” Plugin. 

A “Must Use” Plugin is a perfect solution for setting up Custom Post Types, Taxonomies, Google Analytics, and other important – but not necessarily “updatable” code that would otherwise be lost upon a theme change.

The general consensus among the WordPress elite is: CPT’s & Taxonomies should NOT be handled at the theme level, but rather, at the plugin level. A “Must Use” Plugin is code that cannot be deactivated or deleted unless you have FTP access.

Why not create a normal plugin or use functions.php?

You could. But there are extra steps to get it activated if you’re running a multi-site network. Furthermore, if others have access to the Plugins section of the WP Dashboard, there’s a chance it could be deleted or deactivated by mistake. Functions.php? You loose everything when change themes. By using a “Must Use” plugin, the code will always be available – no matter what network, theme, or curious guest blogger might do otherwise.

Ok, how do I create a “Must Use” Plugin?

  1. You need to create a directory: /wp-content/mu-plugins/
  2. Next, create a PHP file. You can name it anything you want. Mine is named grd_functions.php. The full path would look like: /wp-content/mu-plugins/grd_functions.php.
  3. Make sure you start the contents of the file with a <?php
  4. Now add your code, save your file and upload

That’s it! Really!

Check out the history of Must Use Plugins and learn more at the WordPress Codex

How about an example?

Here is grd_functions.php, which runs this web site:

Each and every time I change themes around here, I don’t have to re-create CPT’s, Taxonomies, Google Analytics, Custom Scripts, etc…Feel free to try my example, and never lose or have to re-write custom code again!

Image Credit: Armand9x

Author: Greg Rickaby

Greg is Director of Engineering at WebDevStudios and author of a children's book titled, Creating a Website: Design and Build Your First Site!.

6 thoughts on “Create a ‘Must Use’ Plugin for WordPress”

  1. I am a beginner using wordpress and I must say this article is a good starting point if you really want to get full control out of your wordpress site. A must read for all beginners. Thanks!

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