Resolving Jetpack and WooCommerce Vendor Account Creation Warnings

If you're seeing a warning about an 'Undefined array key "source"' or a 'headers already sent' error when creating a vendor account on your WooCommerce site, you're not alone. This is a known conflict that can occur between the Jetpack plugin and certain WooCommerce extensions. This guide will explain why it happens and provide the most common solutions to resolve it on your site.

Understanding the Problem

This specific error is typically triggered by a conflict. The Jetpack plugin's WooCommerce Analytics module interacts with the process of creating a new user. Some third-party plugins, particularly those that add vendor or multi-vendor marketplace functionality, customize this user creation process in a way that Jetpack did not initially anticipate. This mismatch can lead to PHP warnings being generated.

The error messages themselves are not usually fatal, but they can break functionality—like the ability to set HTTP headers—which results in the 'headers already sent' error and a failed account creation process. These warnings are primarily visible because WP_DEBUG mode is enabled on the site, which is a common setup on staging or development environments.

How to Fix the Vendor Account Creation Error

Here are the most effective solutions, starting with the simplest and most recommended approach.

Solution 1: Disable WP_DEBUG on Your Live Site (Recommended)

PHP warnings and notices are meant for developers to identify issues during the development phase. They should almost always be hidden on a live, production website to prevent them from interrupting normal site operations and being displayed to users.

1. Access your site's files, either via FTP/SFTP or your web host's file manager.
2. Locate and edit the wp-config.php file in the root directory of your WordPress installation.
3. Find the line that says: define( 'WP_DEBUG', true );
4. Change this line to: define( 'WP_DEBUG', false );
5. Save the file and upload it back to your server if necessary.

This will suppress the on-screen display of warnings and should immediately resolve the 'headers already sent' portion of the error, allowing the vendor account creation process to complete. The underlying warning will still be logged if debug logging is enabled, but it will not interfere with your site's frontend operations.

Solution 2: Check for a Jetpack Plugin Update

Based on user reports, the Jetpack team has acknowledged this conflict and worked on defensive code fixes to prevent it from causing errors. These fixes are included in subsequent plugin updates.

Navigate to Dashboard » Updates in your WordPress admin area and check if an update is available for Jetpack. If one is available, update the plugin and then test to see if the error persists. Keeping all plugins updated is a best practice for security and compatibility.

Solution 3: Temporary Workaround (For Developers)

If you must keep WP_DEBUG enabled and cannot wait for a plugin update, a temporary code fix can be implemented. This involves adding a check to see if the expected array key exists before trying to use it.

Note: This solution involves editing plugin code. Any changes made will be overwritten the next time Jetpack is updated. This is only recommended for developers comfortable with code and should be considered a temporary patch.

The error references the file class-universal.php on line 514. A developer can open that file and modify the problematic code to include a conditional check to prevent the warning.

Conclusion

The 'Undefined array key' warning during vendor signup is a compatibility issue that has been addressed by the Jetpack team in newer versions. For most site owners, the simplest and safest solution is to ensure WP_DEBUG is set to false on a live production site. Always remember to create a complete backup of your website before making any changes to its files or configuration.