WordPress Functions.php File Explained: The Essential Guide

WordPress functions.php file

The WordPress functions.php file is one of the most important operating files of WordPress. At a minimum, two functions.php files exist for every WordPress website: the functions file in WordPress core and an additional functions file in your WordPress theme. Additionally, a child theme will also have a functions.php file.

In this guide, we’ll cover what the functions.php file is, where the WordPress functions.php file is located, how to edit it and more. We’ll also offer a primer on WordPress functions. Let’s dive in.

If you’re reading this article, chances are that you’ve gotten your basic WordPress installation up and running or already have a WordPress website. Everything seems to be working well, and then you want to do what seems like it should be the click of a button. Then you find a tutorial online, and it turns out you need to directly edit the WordPress functions file, or the functions.php file.

Or maybe you’re building your first WordPress theme and have questions about how the functions file should be edited and best practices for WordPress theme development. At the end of this article, you should have a better grasp of how the WordPress functions.php file works and how to best utilize it.

What Is the Functions.php File in WordPress?

The WordPress functions.php file is a powerful operating file that houses important PHP functions that make a WordPress website functional.

There are two primary locations of a functions file within WordPress:

  • The functions.php file located within the main directory of your website that comes packaged with WordPress core files
  • The functions.php file(s) located in your WordPress theme and/or WordPress child theme. Each WordPress theme you have installed has its own file called functions.php in its root within your WordPress installation.

Quite similar to how WordPress plugins work, the functions.php file simply exists to allow users to enter in custom PHP code to execute on pages. This can be used for countless things, from basic added functionality like server-side calculations, to more complex items, like full programs written in PHP for users to take advantage of.

Note: There is a “functions.php” file in every theme you have. While it’s easy enough to change your blog’s theme with one click via WordPress, keep in mind that this will alter the functions.php file.

If you’re someone who enjoys experimenting with various themes, keep in mind that you’ll need to manually migrate any functions.php changes you’ve made. Additionally, some themes may not support newer versions of PHP if they have not been actively maintained, rendering some of your older functions useless.

That’s why even after you decide to alter your theme, it’s important to formally perform QA or simply test everything on your site. Don’t take WordPress’s message that your theme



This article was written by Kristen Wright and originally published on WordPress News and Updates from iThemes – iThemes.

Disclosure: Some of the links in this post are "affiliate links." This means if you click on the link and purchase the product, We may receive an affiliate commission.

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