Plugin could not be activated because it triggered a fatal error WordPress Origin: Application & API Last updated 11 Oct 2026

WordPress: Plugin could not be activated because it triggered a fatal error

Activating the plugin caused a PHP fatal error — usually PHP version incompatibility, a conflict with another plugin/theme, or missing PHP extensions.

Exact message you may see Plugin could not be activated because it triggered a fatal errortriggered a fatal error
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Seen on: WordPress

Meaning

WordPress catches the error during activation. Enable WP_DEBUG_LOG to see the real error in wp-content/debug.log (function redeclared, class not found, syntax error for your PHP version).

Common causes

  • Plugin requires a newer/older PHP version
  • Function/class name conflict with another plugin
  • Missing PHP extension (intl, mbstring, sodium)
  • Corrupted/incomplete upload

⚡ Quick fix

  1. Turn on WP_DEBUG_LOG and read wp-content/debug.log
  2. Check PHP version requirements
  3. Deactivate conflicting plugins and retry

Detailed fix by platform

WordPress

  1. php
    // wp-config.php
define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);

How to diagnose

  1. Log — debug.log error
  2. PHP — Version vs requirements
  3. Conflicts — Other plugins

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Application & API. Errors that are often confused with or caused by this one (click to open):

Allowed memory size exhausted — PHP Fatal error: Allowed memory size of X bytes exhausted (PHP)Allowed memory size e…ArgumentCountError — Fatal error: Uncaught ArgumentCountError: Too few arguments to function foo(), 1 passed and exactly 2 expected (PHP)ArgumentCountErrorCall to member function on null — Fatal error: Uncaught Error: Call to a member function x() on null (PHP)Call to member functi…Call to undefined function — PHP Fatal error: Uncaught Error: Call to undefined function (PHP)Call to undefined fun…Call to undefined function (WordPress) — WordPress: Fatal error: Uncaught Error: Call to undefined function wp_get_current_user() / add_action() / get_header() (WordPress)Call to undefined fun…Call to undefined function create_function() — WordPress on PHP 8: Fatal error: Uncaught Error: Call to undefined function create_function() / each() (WordPress)Call to undefined fun…Cannot redeclare — Fatal error: Cannot redeclare function foo() (previously declared in …) (PHP)Cannot redeclareCritical error — WordPress: There Has Been a Critical Error on This Website (WordPress)Critical errorPlugin co…

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