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Resolving Contact Form 7 Deprecation Warnings: A Guide to PHP 8+ and Tag Generator Issues

17 threads Sep 7, 2025 Plugin → Contact form 7

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If you've recently updated your PHP version or Contact Form 7 and are now seeing deprecation warnings in your error logs, you're not alone. This is a common issue as software evolves to meet modern standards. This guide will explain the two most frequent causes of these warnings and provide actionable steps to resolve them.

Understanding the Two Main Types of Warnings

Based on community reports, the warnings generally fall into two categories:

  1. PHP 8.x Deprecation Warnings: These often mention preg_replace(): Passing null to parameter #3 ($subject) and point to files like formatting.php on lines 606-608.
  2. Tag Generator v1 Deprecation Warnings: These warnings state WPCF7_TagGenerator::add(): Use of tag generator instances older than version 2 is deprecated and often name a specific add-on like 'cf7ascaptcha', 'multiple file upload', or 'password'.

1. Fixing PHP 8.x Null Parameter Warnings

Why This Happens

PHP 8.0 and later became much stricter about data types. Functions like preg_replace() now require a string or array for the $subject parameter and will throw a deprecation warning if they receive a null value. This typically occurs when a form field, through custom code or a third-party add-on, is passing a null value to a CF7 formatting function.

How to Resolve It

  1. Identify the Source: The warning is a symptom, not the cause. The null value is coming from elsewhere. Enable debugging (WP_DEBUG_LOG) and check your logs for a stack trace that shows which function or plugin is sending the null value.
  2. Check Your Add-ons: This issue is frequently triggered by other plugins that extend Contact Form 7. Check for updates for all your CF7-related extensions, especially conditional field or database plugins.
  3. Review Custom Code: If you have custom code snippets that modify CF7 field values, audit them to ensure they are not returning null under certain conditions.
  4. Update Everything: Ensure your core Contact Form 7 plugin is updated to the latest version, as the development team has been addressing these compatibility issues.

2. Fixing Tag Generator v1 Deprecation Warnings

Why This Happens

With the release of Contact Form 7 version 6.0, a new Tag Generator API (version 2) was introduced. The old version 1 API was marked as deprecated. This means it still works but now generates warnings to encourage developers to update their code. The warning explicitly names the plugin using the old API (e.g., 'cf7ascaptcha', 'math-captcha', 'Use-your-Drive').

How to Resolve It

This warning must be fixed by the developer of the named plugin. As a site owner, you cannot directly resolve this yourself.

  1. Identify the Plugin: Note the name of the plugin mentioned in the warning message in your logs (e.g., 'cf7msb_honeypot', 'password').
  2. Check for Updates: Visit the WordPress Plugin Directory or the developer's website to see if an updated version of the add-on that supports Tag Generator v2 is available. Install it.
  3. Contact the Developer: If no update is available, contact the support channel for that specific plugin and politely inform them of the deprecation warning. Point them to the CF7 6.0 release notes for reference.
  4. Seek an Alternative: If the plugin is abandoned and causing critical issues, you may need to find a alternative plugin that provides similar functionality and is actively maintained.

Conclusion

While deprecation warnings can look alarming, they are often notices rather than critical errors that break your site. The solution almost always involves updating software—either the core Contact Form 7 plugin, your PHP version, or the third-party add-ons you use alongside it. By systematically identifying the source of the warning and taking the steps outlined above, you can keep your forms running smoothly and your error logs clean.

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