Resolving the WooCommerce Payments and Max Mega Menu Conflict

A common and disruptive issue for WordPress site administrators is encountering a critical error when trying to access the Appearance > Menus screen. This problem frequently manifests alongside a specific PHP error in the server logs, pointing to a conflict between two popular plugins: Max Mega Menu and WooCommerce Payments.

Understanding the Problem

When both plugins are active, navigating to the menu management area can trigger a PHP Fatal error: Uncaught TypeError: array_merge(): Argument #1 must be of type array, null given. The error consistently originates from a file within the WooCommerce Payments plugin, typically around line 558-564 in the class-wc-payments-admin.php file.

This is a plugin conflict, not a flaw in one single plugin. The issue arises because the WooCommerce Payments plugin attempts to load its scripts on admin pages where it expects certain data to be present in a specific format. The Max Mega Menu plugin alters the admin environment in a way that can sometimes return a null value where an array is expected, causing the PHP error that breaks the page.

How to Resolve the Conflict

There are several proven solutions to this problem. It is recommended to try them in order.

Solution 1: Update Your Plugins

The first and most important step is to ensure all your plugins, especially WooCommerce Payments and Max Mega Menu, are updated to their latest versions. Development teams for both plugins are typically aware of common conflicts and often release patches and compatibility fixes. This is the easiest and most effective solution if an update is available.

Solution 2: Check for a Patch from WooCommerce Payments

This specific conflict has been widely reported. The WooCommerce Payments team has addressed it in their plugin's update cycle. If you are experiencing this error, it is highly likely that updating WooCommerce Payments will resolve it immediately. This confirms that the core fix often resides in an update to the Payments plugin.

Solution 3: Temporary Deactivation (For Diagnosis)

If updating does not work, you can perform a quick diagnosis to confirm the conflict:

1. Go to Plugins > Installed Plugins.
2. Temporarily deactivate the WooCommerce Payments plugin.
3. Try to access Appearance > Menus again. If the page loads without error, you have confirmed the conflict.
4. Reactivate WooCommerce Payments. The error may be resolved if a recent update was installed during this process.

Solution 4: Enable Debugging to Get Detailed Errors (Advanced)

If the problem persists and you need more information, enabling WordPress debugging can provide a more detailed error message, which can be helpful for advanced troubleshooting or when seeking support from community forums.

Warning: This should only be done on a development or staging site, as displaying errors on a live site is a security risk. To enable debugging, edit your wp-config.php file and ensure the following lines are set:

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true ); // Errors are logged to wp-content/debug.log
define( 'WP_DEBUG_DISPLAY', false ); // Prevents errors from being shown on screen

After reproducing the error, check the wp-content/debug.log file for more precise details.

Conclusion

The conflict between Max Mega Menu and WooCommerce Payments is a classic example of how two well-coded plugins can sometimes interfere with each other in the WordPress admin. The primary resolution path is almost always to update the WooCommerce Payments plugin to the latest version, as their development team has implemented fixes for this exact issue. Keeping all plugins and themes updated is the best practice for preventing such conflicts and maintaining a secure, stable website.