On WordPress website hosted on Plesk for Linux server, pagination buttons in WordPress Admin dashboard do not work as expected

Symptoms

• On a WordPress website hosted on a Plesk for Linux server, pagination buttons in WordPress Admin dashboard do not work as expected.

• HTTP/3 is enabled.

• PHP handler on the domain is set as FPM application served by nginx in the menu Domains > example.com > PHP.

• When WordPress debug mode enabled, the following PHP warning appears on the website:

  PHP Warning: Undefined array key "HTTP_HOST" in /var/www/vhosts/example.com/httpdocs/wp/wp-admin/includes/misc.php

Cause

nginx processing the variable HTTP_HOST differently when serving HTTP/3 requests:
https://trac.nginx.org/nginx/ticket/2281

Resolution

1. Connect to the server via SSH.

2. Create or edit file /etc/nginx/fastcgi.conf and add the following configuration to it:

   fastcgi_param HTTP_HOST $host;

3. Restart nginx to apply the changes:

   # service nginx restart