Title: Error when upgrading to PHP8
Last modified: December 15, 2020

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# Error when upgrading to PHP8

 *  Resolved [Per Olsson](https://wordpress.org/support/users/styrketrappan/)
 * (@styrketrappan)
 * [5 years, 6 months ago](https://wordpress.org/support/topic/error-when-upgrading-to-php8/)
 * I get this when testing an upgrade to PHP8:
 * Warning
    : Undefined array key “hierarchical” in /home/styrketr/public_html/wp-
   content/plugins/sensei-lms/widgets/class-sensei-course-categories-widget.php
 * The categories are still listed and looks nice, however I rolled back to PHP7.4
   since I tested on a production site (I did not setup a staging for this purpose,
   which I know I should) and there are several plugins not yet compatible.

Viewing 2 replies - 1 through 2 (of 2 total)

 *  Plugin Author [Donna Peplinskie (a11n)](https://wordpress.org/support/users/donnapep/)
 * (@donnapep)
 * [5 years, 5 months ago](https://wordpress.org/support/topic/error-when-upgrading-to-php8/#post-13881870)
 * Thanks for the report Per. Indeed, we have not yet tested to ensure compatibility
   with PHP 8. I’ve added a comment to the existing [PHP 8 compatibility issue](https://github.com/Automattic/sensei/issues/3773).
 *  Thread Starter [Per Olsson](https://wordpress.org/support/users/styrketrappan/)
 * (@styrketrappan)
 * [5 years, 5 months ago](https://wordpress.org/support/topic/error-when-upgrading-to-php8/#post-13882287)
 * [@donnapep](https://wordpress.org/support/users/donnapep/) lovely!

Viewing 2 replies - 1 through 2 (of 2 total)

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 * 2 replies
 * 2 participants
 * Last reply from: [Per Olsson](https://wordpress.org/support/users/styrketrappan/)
 * Last activity: [5 years, 5 months ago](https://wordpress.org/support/topic/error-when-upgrading-to-php8/#post-13882287)
 * Status: resolved