Can't edit categories

I wanted to edit the descriptions of some of my categories, but ClassicPress breaks when I click on ‘Edit’ - I get a blank screen in my CP admin. Is this a known bug, or something related to my setup? I tried with different themes enabled, so that shouldn’t really be the issue.

Could be a plugin conflict. Try disabling each plugin and rechecking to find the culprit, better with error logging enabled.

EDITED TO ADD: just confirmed (My CP is on PHP8, and I have some WP plugins installed and a theme that the dash marks as installable from the WP repo). I need to investigate further because it is not likely we have the same environment and setup. So it might be a problem with CP.

@viktor and @MattyRob I will post here my results as soon as I understand what is going on so that you can check.

hmmm… same here

CP 1.5.0

all http status codes are 200 when the page loads - - i’ll try more troubleshooting later

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it doesn’t seem to be a plugin, I disabled all of them and the same thing happens. No errors in the console apart from a shield plugin same site cookie and I have the 2015 CP version on for the theme, just to test if it was the theme. Going to enable logging to see if there is something wrong there.

And bingo, we do have a fatal.

Fatal error: Uncaught Error: Call to undefined function is_taxonomy_viewable() in ***/wp-includes/admin-bar.php:731 Stack trace: #0 ***/wp-includes/class-wp-hook.php(287): wp_admin_bar_edit_menu() #1 ***/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters() #2 ***/wp-includes/plugin.php(524): WP_Hook->do_action() #3 ***/wp-includes/admin-bar.php(86): do_action_ref_array() #4 ***httpdocs/wp-includes/class-wp-hook.php(287): wp_admin_bar_render() #5 ***/httpdocs/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters() #6 ***/wp-includes/plugin.php(458): WP_Hook->do_action() #7 ***/wp-admin/admin-header.php(230): do_action() #8 ***/wp-admin/term.php(68): require_once('...') #9 {main} thrown in ***/wp-includes/admin-bar.php on line 731

The culprit seems to be the admin-bar.php and admin-header.php but being not so confident I leave the interpretation to the experienced devs.

@adastra @classyMan

I’m sorry about that. It’s a known issue that was reported, and we already have a fix scheduled for 1.5.1 coming soon:

A temporary fix to make the edit page work is to add the following code to your theme’s functions.php:

if ( ! function_exists( 'is_taxonomy_viewable' ) ) :
function is_taxonomy_viewable( $taxonomy ) {
	if ( is_scalar( $taxonomy ) ) {
		$taxonomy = get_taxonomy( $taxonomy );
		if ( ! $taxonomy ) {
			return false;
	return $taxonomy->publicly_queryable;

Please let me know if you run into any issues.


Same here, was gonna ask if it was me or the code, i had assumed it was me because my code is normally quite drunk and disorderly.


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