How to Fix Critical Errors When Deactivating or Activating Polylang

Encountering a critical error or a white screen when trying to activate or deactivate the Polylang plugin is a common issue reported by WordPress users. This problem can be frustrating, as it often locks you out of your dashboard or prevents you from making changes to your site's language setup. Based on community reports and troubleshooting patterns, this article explains why these errors occur and provides the most effective solutions.

Why Do These Critical Errors Happen?

Contrary to what it may seem, a critical error that occurs the moment you deactivate Polylang is almost never caused by the plugin itself. This is because a deactivated plugin is completely unloaded by WordPress; its code does not run. The error is typically triggered by something else on your site that is trying to use Polylang's functions even after the plugin is gone.

The most common culprits are:

• Custom Code in Your Theme: Functions.php file or a custom theme module that calls a Polylang function without first checking if the plugin is active.
• A Page Builder or Another Plugin: Some themes or plugins, like Bricks or WooCommerce in certain versions, may have code that depends on Polylang.
• Residual Configuration: In rare cases, data left behind from a partial uninstallation can cause conflicts.

Similarly, activation errors can be caused by conflicts with other plugins or your theme, especially if they are not fully compatible with the current version of Polylang.

How to Troubleshoot and Fix the Issue

Follow these steps to identify the source of the error and regain control of your site.

Step 1: Regain Access to Your Dashboard

If the error is blocking your WordPress admin dashboard, you will need to deactivate Polylang manually. You can do this by using one of two methods:

• Via FTP/SFTP or File Manager: Connect to your site's server and navigate to the wp-content/plugins directory. Locate the polylang folder and rename it to something like polylang_deactivated. This will force WordPress to deactivate the plugin.
• Via Database (Advanced): You can also deactivate all plugins by editing the active_plugins option in your wp_options table using phpMyAdmin. This is a more advanced method and should be done with caution.

Step 2: Enable Debugging to Find the Root Cause

To see the specific error message that is causing the problem, you need to enable WordPress debugging. Add the following lines to your wp-config.php file (you can access this file via FTP):

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );

After adding these lines, try to activate or deactivate Polylang again. The error details will be written to a log file called debug.log in your wp-content directory. This file will tell you exactly which PHP file is causing the fatal error.

Step 3: Identify and Fix the Problematic Code

Open the debug.log file and look for the error. It will often point to a specific file in your theme or another plugin.

• If it's your theme: Contact your theme's support and provide them with the error message. They should update their code to check if Polylang is active before using its functions. A properly coded theme should use a conditional check like if ( function_exists( 'pll_get_post' ) ) { ... }.
• If it's another plugin: Check the plugin's support forums or contact its developers to report the compatibility issue.
• If you have custom code: Review any custom code you have added (e.g., in your child theme's functions.php) and wrap any calls to Polylang functions (e.g., pll__(), pll_current_language()) with the function_exists() check.

Step 4: Completely Uninstall Polylang (If Desired)

If your goal is to remove Polylang entirely, you must properly uninstall it to remove its data from your database. The Polylang team provides documentation on how to do this. Simply deactivating and deleting the plugin does not automatically remove all of its configuration data, which can sometimes lead to issues.

Conclusion

A critical error during Polylang activation or deactivation is almost always a sign of a dependency elsewhere in your site's code. By enabling debugging to find the exact error and then addressing the root cause in your theme or another plugin, you can resolve this issue and successfully manage your Polylang installation.