How To Add a Plugin Function Into a WordPress Theme Correctly

I recently deactivated a plugin on a WordPress website only to find that it stopped working. On the home page, only an error was displayed. The error told me that I was trying to call some function that didn’t exist. Clearly, the function disappeared because of the deactivation of plugin. To check my theory, I re-activated the plugin and the website started working again.

The plugin I deactivated was related post plugin, and when I checked the theme files, there was a call to the function,

<?php related_posts(); ?>

I removed that function call and deactivated the plugin, which fixed the issue.

I am sure that you must have came across the same same issue in the past. The solution to the issue is to add plugin functions into a theme correctly, which is,

<?php if(function_exists('function_name'))
{
function_name();
}
?>

As you can see in the code snippet above, an if condition is used to check if the function exists. If it doesn’t exist, then it won’t be called, thus preventing the WordPress website from breaking completely in case the plugin that has that function is disabled.

So, to call related_posts function, the following code should be added to the theme theme’s template files,

<?php if(function_exists('related_posts'))
{
related_posts();
}
?>

Now, even if the related posts plugin is deactivated, it won’t affect the website.

If you are a WordPress developer and you want to integrate a plugin with a theme, or if you are a WordPress user who need to add a plugin’s function to a theme file, then make sure to add the function call in the correct way.