Understanding and Managing PHP Deprecation Warnings in Site Kit by Google

If you're running a modern version of PHP (8.1 or higher) with the Site Kit by Google plugin, you may have noticed your server's debug log filling up with deprecation warnings. This is a common experience for many users, and this guide will help you understand why it happens and what you can do about it.

What Are These PHP Deprecation Warnings?

PHP deprecation warnings are messages generated by the PHP engine to alert developers that a piece of code uses a feature or function that will be removed in a future version of PHP. These are not errors; they are advance notices meant to encourage developers to update their code for future compatibility.

Common warnings seen with Site Kit include:

• Creation of dynamic property ... is deprecated
• Calling get_class() without arguments is deprecated
• Passing null to parameter #1 ($string) of type string is deprecated (often for strtotime(), ltrim(), or htmlspecialchars())
• Implicitly marking parameter ... as nullable is deprecated (common in PHP 8.4)

Why Do These Warnings Appear with Site Kit?

It's important to understand that the vast majority of these warnings do not originate from the core Site Kit plugin itself. They are almost exclusively generated by third-party libraries and dependencies that the plugin bundles to communicate with Google's services (e.g., the Google API PHP Client library).

The Site Kit by Google team is consistently working to update these bundled dependencies in new plugin releases to address these warnings. However, because the warnings do not affect the plugin's core functionality—data is still collected and displayed correctly—they are often prioritized as a code cleanup task rather than a critical bug fix.

Do These Warnings Affect My Site's Performance?

No. This is the most crucial point. These deprecation notices are informational only. They do not impact the functionality, performance, or stability of your WordPress site or the Site Kit plugin. Your analytics, Search Console, and other data will continue to be tracked and reported accurately.

The primary issue is that these messages can rapidly fill up your server's debug log (debug.log), consuming disk space.

Common Solutions and Workarounds

1. For Most Users: Disable Debug Logging (Recommended)

If your site is functioning normally and you only see these warnings in logs, the simplest solution is to turn off WordPress debug logging. This is the recommended approach for most site owners, as keeping debug logs active on a production site is generally unnecessary and can be a security risk.

In your wp-config.php file, ensure the following lines are set:

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

2. For Developers: Suppress Deprecation Warnings

If you need to keep logging enabled for other reasons but want to silence just the deprecation notices, you can modify the error reporting level in your wp-config.php file. Add the following line:

error_reporting( E_ALL ^ E_DEPRECATED );

This tells PHP to report all error types except for deprecation warnings.

3. Keep Site Kit Updated

The Site Kit by Google team regularly releases updates that include updated dependencies. Ensure you are always running the latest version of the plugin, as many reported warnings are fixed in subsequent releases.

4. For a Specific, Function-Breaking Error

While extremely rare, the sample threads did show one instance of a fatal error (PHP Fatal error: Call to a member function is_type() on string). This type of error is different from a deprecation warning and will break functionality. If you encounter a fatal error, it is a genuine bug that should be reported. You can temporarily revert to a previous version of the plugin until a fix is released.

When to Be Concerned

You only need to take further action if:

• You encounter a fatal error that causes a white screen of death or breaks site functionality.
• The warnings are being displayed directly on your site's pages or dashboard for users to see (this indicates your server's PHP configuration has display_errors enabled, which is not recommended for a live site).
• The Site Kit plugin stops working entirely (e.g., disconnects, fails to show data).

In these specific cases, the issue is likely related to your server's PHP configuration rather than the plugin's deprecation warnings. You should contact your web hosting provider for assistance in configuring appropriate error reporting levels for a production environment.

The Bottom Line

PHP deprecation warnings with Site Kit are a known and largely cosmetic issue. The plugin continues to work perfectly despite these log entries. The best course of action for most site owners is to disable debug logging on their production site and rest assured that their data tracking is unaffected.