Error after switching themes on wordpress

[pranav1326]

When I try to switch a theme this error happens. And after this error whole, WordPress is not working or even opening. I have uninstalled and reinstalled WordPress once but the same thing happened. I searched on google and I find out this is because of PHP version 8.

Fatal error: Uncaught ArgumentCountError: array_merge() does not accept unknown named parameters in C:\xampp\htdocs\wordpress\wp-includes\widgets.php:1265 

Stack trace:
#0 C:\xampp\htdocs\wordpress\wp-includes\widgets.php(1265): array_merge(wp_inactive_widgets: Array, sidebar-1: Array, footer-1: Array, footer-2: Array, footer-3: Array)
#1 C:\xampp\htdocs\wordpress\wp-includes\widgets.php(1220): retrieve_widgets(true) 
#2 C:\xampp\htdocs\wordpress\wp-includes\class-wp-hook.php(289): _wp_sidebars_changed('Twenty Twenty') 
#3 C:\xampp\htdocs\wordpress\wp-includes\class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array) 
#4 C:\xampp\htdocs\wordpress\wp-includes\plugin.php(478): WP_Hook->do_action(Array) 
#5 C:\xampp\htdocs\wordpress\wp-includes\theme.php(3267): do_action('after_switch_th...', 'Twenty Twenty', Object(WP_Theme)) 
#6 C:\xampp\htdocs\wordpress\wp-includes\class-wp-hook.php(287): check_theme_switched() 
#7 C:\xampp\htdocs\wordpress\wp-includes\class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array) 
#8 C:\xampp\htdocs\wordpress\wp-includes\plugin.php(478): WP_Hook->do_action(Array) 
#9 C:\xampp\htdocs\wordpress\wp-settings.php(546): do_action('init') 
#10 C:\xampp\htdocs\wordpress\wp-config.php(90): require_once('C:\xampp\htdocs...') 
#11 C:\xampp\htdocs\wordpress\wp-load.php(37): require_once('C:\xampp\htdocs...') 
#12 C:\xampp\htdocs\wordpress\wp-blog-header.php(13): require_once('C:\xampp\htdocs...')
#13 C:\xampp\htdocs\wordpress\index.php(17): require('C:\xampp\htdocs...') 
#14 {main} thrown in C:\xampp\htdocs\wordpress\wp-includes\widgets.php on line 1265

There has been a critical error on your website.

[dkarfa]

Hi @pranav1326,

Thanks for the reporting this and welcome to WordPress Trac. I am reviewing it.

Thank you,
Deb

[hellofromTonya]

Hello @pranav1326 and Welcome to Trac!

Thank you for reporting this issue.

Are you running WordPress 5.6 RC4? If no, what version of WordPress is running on your website?

[hellofromTonya]

Ticket #50913 with changeset 48839 added a PHP 8 fix for ArgumentCountError: array_merge() does not accept unknown named parameters in includes/widgets.php.

[hellofromTonya]

Can reproduce the exact fatal error when running PHP 8 with WP 5.5.3.
Cannot reproduce when running PHP 8 with WP 5.6 RC4.

[SergeyBiryukov]

Hi there, welcome to WordPress Trac! Thanks for the report.

As noted above, this was fixed in [48839] / #50913.

For some context, ​WordPress 5.5 was released in August, and ​PHP 8.0 only a week ago.

WordPress 5.6 (coming up on ​December 8) is the first version that ​aims for (beta) compatibility with PHP 8.0.

[pranav1326]

Replying to hellofromTonya:

Hello @pranav1326 and Welcome to Trac!

Thank you for reporting this issue.

Are you running WordPress 5.6 RC4? If no, what version of WordPress is running on your website?

I am using currently WordPress version 5.5.3

[pranav1326]

Thank you so much guys for your responses. The issue has been solved [48839] by this ticket.