{"id":37708,"date":"2022-10-25T07:00:06","date_gmt":"2022-10-25T14:00:06","guid":{"rendered":"https:\/\/dhblog.dream.press\/blog\/?p=37708"},"modified":"2026-08-22T14:53:03","modified_gmt":"2026-08-22T21:53:03","slug":"guide-to-wp-functions","status":"publish","type":"post","link":"https:\/\/www.dreamhost.com\/blog\/guide-to-wp-functions\/","title":{"rendered":"Everything You Need to Know About the WordPress functions.php File"},"content":{"rendered":"\n

A WordPress theme can include one small file that changes how your whole site behaves. The WordPress functions.php<\/i> file \u2014 also known as the functions file \u2014 is a PHP file in your theme\u2019s folder that works much like a plugin: WordPress loads it automatically along with your active theme, and any custom PHP code you add to it runs on both the front end and the admin side of your site.<\/b> You\u2019ll find it at wp-content\/themes\/your-theme\/functions.php<\/i>.<\/p>\n\n\n\n

That makes the functions file a perfect place to start with WordPress development<\/a>. By editing this one file, you can add Google Analytics to your site, create custom menus, or display a post\u2019s estimated reading time \u2014 no extra plugin required. In this guide, we\u2019ll explain how the file works, show you 2 safe ways to edit it, and share 8 practical code snippets you can copy today.<\/p>\n\n\n\n

What Is the functions.php File?<\/b><\/h2>\n\n\n\n

The functions.php<\/i> file is one of WordPress\u2019s standard theme files \u2014 technically optional, and easy to create yourself if your theme doesn\u2019t have one. To the untrained eye, it may not look like much, but the functions file is a powerful tool that enables you to do a lot of interesting things:<\/p>\n\n\n

\n
\"WordPress<\/figure>\n<\/div>\n\n\n

The WordPress Theme Handbook<\/a> describes the functions file like this:<\/p>\n\n\n\n

\u201cThe functions.php essentially acts like a WordPress plugin, letting you add custom PHP functions, classes, interfaces, and more. It opens up the entirety of the PHP programming language to your theme.\u201d<\/p>\n\n\n\n

In simple terms, the functions file enables you to add custom code to your site. It lets you create new functions or reference existing ones in customized ways. As the handbook points out, this makes the functions file very similar to a plugin \u2014 but there are some differences between the two.<\/p>\n\n\n\n

The most important difference is that the functions file belongs to a specific theme. For a standalone active theme, WordPress loads that theme\u2019s functions.php. When a child theme is active, WordPress loads both the child and parent functions.php files. If you switch away from that theme, its custom code stops running, and a theme update can overwrite edits made directly to that theme\u2019s files.<\/p>\n\n\n\n

For this reason, you should consider creating a child theme<\/a> and adding your code to the child\u2019s functions file instead. WordPress loads a child theme\u2019s functions.php just before the parent theme\u2019s, so your customizations keep running \u2014 and survive parent theme updates.<\/p>\n\n\n\n

The Theme Handbook\u2019s rule of thumb is that themes should only deal with the site\u2019s design. If you\u2019re building a feature that should stick around no matter what your site looks like, it\u2019s best practice to create a plugin<\/a> for it. For design-tied tweaks, the functions file is fair game \u2014 the choice is yours. For now, let\u2019s look at the different ways you can edit your functions file!<\/p>\n\n\n\n

Where Is the functions.php File Located?<\/b><\/h3>\n\n\n\n

Your theme\u2019s functions file lives in the root of the theme\u2019s own folder: wp-content\/themes\/your-theme\/functions.php<\/i>. If you use a child theme, the child keeps its own separate functions.php<\/i> in its folder. If the file doesn\u2019t exist, create it there and put <?php<\/i> on the first line before adding PHP snippets; WordPress will load it automatically.<\/p>\n\n\n\n

How to Edit the Functions File (2 Methods)<\/b><\/h2>\n\n\n\n

Editing your functions file is easy when using a standard text editor, like TextEdit or Notepad. However, before you get started, it is vitally important that you create a backup<\/a> of your site and save the original, unedited functions.php<\/i> file. This will enable you to restore your website if something goes wrong during the editing process. (Even safer: test your changes on a staging copy of your site first. DreamPress<\/a>, DreamHost\u2019s managed WordPress hosting, includes 1-Click Staging on every plan for exactly this.)<\/p>\n\n\n\n

1. Use the WordPress Editor<\/b><\/h3>\n\n\n\n

If you have access to the WordPress admin interface, you can edit the functions file directly from the Theme File Editor. Go to Appearance > Theme File Editor<\/i>:<\/p>\n\n\n

\n
\"WordPress<\/figure>\n<\/div>\n\n\n

On the right-hand side of the screen, you will see a list of all your theme files. These differ depending on which theme you use, but one of the options should be Theme Functions<\/i> (functions.php<\/i>).<\/p>\n\n\n\n

Simply click on the file to open it in the editor:<\/p>\n\n\n

\n
\"WordPress<\/figure>\n<\/div>\n\n\n

Now, you can edit the file directly. Don\u2019t forget to click on Update File<\/i> at the bottom to save your changes when you\u2019re done.<\/p>\n\n\n\n

One warning from WordPress\u2019s own documentation<\/a>: the Theme File Editor doesn\u2019t make backup copies. If a change crashes your site, you can\u2019t use the editor to fix it \u2014 you\u2019ll need the second method below to restore your saved copy of the file.<\/p>\n\n\n\n

2. Access the File Through FTP<\/b><\/h3>\n\n\n\n

If you are unable to use the admin dashboard or prefer to configure files directly, you can also access the functions file using a Secure File Transfer Protocol (SFTP) client <\/a>such as FileZilla<\/a>.<\/p>\n\n\n\n

Open your SFTP client and enter your hosting credentials to connect to your site. To find the right file, navigate to wp-content\/themes\/[the name of your theme]<\/i>. When you open this folder, you\u2019ll see the functions.php<\/i> file:<\/p>\n\n\n

\n
\"editing<\/figure>\n<\/div>\n\n\n

All you have to do now is to edit it using your preferred text editing software. When you\u2019re done, save the file and overwrite it with the exact same name and extension.<\/p>\n\n\n\n

8 Tricks You Can Accomplish With the WordPress Functions File<\/b><\/h2>\n\n\n\n

You should now be ready to start editing your functions file. To get you started, we\u2019ll look at some changes that you can make. All you need to do is copy the provided code snippets and paste them on a new line at the very bottom of your functions file (don\u2019t forget to save it!).<\/p>\n\n\n\n

One tip from the Theme Handbook before you paste anything: if your functions file ends with a closing ?><\/i> tag, leave it out. Stray whitespace after that tag is a classic cause of the WordPress \u201cwhite screen of death,\u201d and skipping the closing tag altogether is perfectly valid PHP \u2014 and standard practice.<\/p>\n\n\n\n

1. Add Google Analytics to Your Site<\/b><\/h3>\n\n\n\n

Google Analytics 4 (which replaced Universal Analytics<\/a> \u2014 standard Universal Analytics properties stopped processing data back in July 2023) tracks your site through the Google tag: a snippet of code that needs to load on every page. Because analytics should keep working when you switch themes, a plugin or site-level integration is the safer production choice. If you use functions.php, the example below hooks the tag into the active theme\u2019s header and will stop working when you switch themes.<\/p>\n\n\n\n

First, grab your tag from Google Analytics. Go to Admin > Data streams<\/i>, click your web data stream, then choose View tag instructions > Install manually<\/i> and copy the Google tag code<\/a> \u2014 it begins with <!– Global tag (gtag.js) –><\/i> and already contains your tag ID (the one that usually starts with \u201cG-\u201d).<\/p>\n\n\n\n

Then paste this wrapper at the bottom of your functions file:<\/p>\n\n\n\n

add_action('wp_head', 'wpb_add_googleanalytics');\n\nfunction wpb_add_googleanalytics() { ?>\n\n<!-- Replace this line with your Google tag (gtag.js) snippet -->\n\n<?php }<\/pre>\n\n\n\n
Swap the placeholder line for the Google tag snippet you copied, save the functions file, and every page on your site will load the tag. If you\u2019re moving over from an old Universal Analytics setup, our guide to switching from Universal Analytics to GA4<\/a> walks through the whole migration.<\/p>\n\n\n\n
\n\n\n
Get Content Delivered Straight to Your Inbox<\/h2>
Subscribe now to receive all the latest updates, delivered directly to your inbox.<\/p>
<\/div>