The wc_current_theme_is_fse_theme function is deprecated

Hi @chumidor ,

Thanks so much for reaching out, and I totally get how those deprecation notices can feel a bit overwhelming in your logs.

Just to share some quick context: the wc_current_theme_is_fse_theme() function is a WooCommerce wrapper that’s now deprecated as of version 9.9. Behind the scenes, it simply calls wp_is_block_theme(), but starting with this update, WooCommerce logs a deprecation notice anytime that older function is used.

That’s likely why you’re seeing messages like this in your logs:

PHP Deprecated: Function wc_current_theme_is_fse_theme() is deprecated since version 9.9.0! Replace with wp_is_block_theme().

If you’re not sure where this is coming from, a good first step is to try temporarily deactivating your plugins one by one and check if the message disappears — that can help narrow down which plugin might still be using the deprecated function.

You could also install the Query Monitor plugin, which is great for catching where specific notices or warnings are coming from.

If you’d rather not dive into plugin testing right now, there’s also a quick way to suppress those deprecation messages so they don’t flood your logs. You can add this snippet either to your theme’s functions.php file, or use the Code Snippets plugin to add it safely:

add_filter( 'deprecated_function_trigger_error', '__return_false' );

Let us know how things go after giving that a try!

Hi @chumidor ,

Thanks for the update!

Just checking — were you able to track down which plugin might be causing that notice?

I added this to the function php snippets area but it did nothing to stop the logging of it

If that doesn’t do the trick, you can try using a Must-Use (MU) plugin. These load before regular plugins, so they’re great for things like suppressing deprecated notices early in the process.

Here’s how you can set it up:

1. Create a folder called mu-plugins inside your wp-content directory (if it doesn’t already exist).
2. Inside that folder, create a file named disable-deprecations.php.
3. Add the following code to that file:

<?php
// Run early to suppress PHP deprecated notices, including WooCommerce's
error_reporting(E_ALL & ~E_DEPRECATED & ~E_USER_DEPRECATED);
add_filter('deprecated_constructor_trigger_error', '__return_false');
add_filter('deprecated_function_trigger_error', '__return_false');
add_filter('deprecated_file_trigger_error', '__return_false');
add_filter('deprecated_argument_trigger_error', '__return_false');
add_filter('deprecated_hook_trigger_error', '__return_false');

Once that’s in place, it should help suppress those notices.

Give it a try and let us know how it goes!

Hi @chumidor,

Thanks for the update, and I appreciate you giving those steps a try!

At this point, since the suppression methods haven’t worked, the best way forward is to pinpoint the source of the deprecation notice directly. Here’s what I recommend:

• Search for wc_current_theme_is_fse_theme in your site files — if you’re comfortable accessing your site via FTP or your hosting file manager, try searching through /wp-content/plugins/ and /wp-content/themes/. A local code editor with “Find in files” can also make this easier.
• Run a conflict test — try deactivating your plugins one at a time and checking if the log stops growing. Once it does, the last plugin deactivated is likely the one still using the deprecated function.

Once you’ve identified the plugin, you can either reach out to its developer to report the deprecated usage or temporarily comment it out manually if you’re confident with code changes.

Thank you. Let us know what you find out.