BugWP logo BugWP
Back to Community
Home / Community / Plugin → Mailchimp for woocommerce

Fixing Common PHP Warnings and Errors in Mailchimp for WooCommerce

27 threads Sep 16, 2025 Plugin → Mailchimp for woocommerce

Content

If you're running the Mailchimp for WooCommerce plugin, you might have encountered PHP warnings or errors in your server logs. These messages are common, especially after updating your PHP version or using non-standard currency codes. This guide will help you understand the most frequent issues and how to resolve them.

Common PHP Warnings and Their Causes

Based on community reports, the most common PHP warnings include:

  • Undefined array key warnings: These often occur when the plugin code attempts to access an array element that doesn't exist. Examples include warnings about undefined keys like 'detail', 'errors', 'path', or 'SERVER_NAME'. These are particularly common on PHP 8.0+ which has stricter error handling.
  • Non-numeric value encountered: This warning typically appears when mathematical operations are performed on non-numeric values, often in cart or campaign processing files.
  • Deprecated function warnings: These occur when the plugin uses functions or methods that are no longer recommended in newer versions of WooCommerce or PHP.
  • Currency code errors: The error "not a valid ISO 4217 currency code" appears when using non-standard currencies like cryptocurrency ('ADA') or reward points ('Points').

How to Troubleshoot and Resolve These Issues

1. Update the Plugin

The first and most important step is to ensure you're running the latest version of Mailchimp for WooCommerce. The development team has addressed many PHP compatibility issues in recent updates. For instance, the 'Undefined array key "detail"' warning was reportedly fixed in version 2.5.4.

2. Check for Conflicting Plugins

Some warnings might be caused by conflicts with other plugins. To test for conflicts:

  1. Temporarily switch to a default WordPress theme (like Twenty Twenty-Four).
  2. Deactivate all plugins except WooCommerce and Mailchimp for WooCommerce.
  3. Check if the warnings persist. If they disappear, reactivate your plugins one by one to identify the culprit.

3. Currency Code Solutions

If you're using a non-standard currency and encountering the "not a valid ISO 4217 currency code" error, you have a few options:

  • Switch to a standard currency (like USD) for the initial plugin setup and synchronization, then switch back to your preferred currency.
  • For reward points systems, consider whether reporting accurate currency values to Mailchimp is essential for your needs.
  • Note that cryptocurrency codes are not currently supported by Mailchimp's API requirements.

4. Server Configuration Issues

Some warnings relate to server settings. The warning about allow_url_fopen=0 indicates that your server configuration restricts certain URL handling functions. While this setting is often recommended for security, the plugin team has acknowledged this issue and planned to address it by implementing cURL as a more compatible alternative.

5. When to Ignore Warnings

Some warnings, particularly those labeled as "Deprecated" or appearing in CLI environments, might not affect functionality. In production environments, you might consider configuring PHP to not display these warnings while keeping error logging active for more critical issues.

When to Seek Further Help

If you've tried these solutions and continue to experience issues:

  • Enable Remote Diagnostics in the plugin's Settings tab to help developers investigate.
  • Check that you're using the correct plugin - some errors reference 'woocommerce-mailchimp' which is a different plugin than 'mailchimp-for-woocommerce'.
  • Provide specific details when seeking help: your plugin version, PHP version, WooCommerce version, and the exact error message.

Most PHP warnings don't prevent the plugin from functioning but should be addressed for optimal performance and compatibility, especially when upgrading PHP versions. The Mailchimp for WooCommerce team has generally been responsive to these community-reported issues and has incorporated fixes in subsequent updates.

Related Support Threads Support