Resolve WordPress Theme PHP Error

I’m running a WordPress site whose theme now throws a PHP error whenever it loads. The problem appeared after I upgraded to the current WordPress version on a server running PHP 8.3, so it’s clearly a compatibility issue. Right now the front-end layout is broken and I can only reach wp-admin through recovery mode.

I need a developer who can:
• Trace and eliminate the PHP error in the theme code.
• Make the theme fully compatible with the latest WordPress core and PHP 8.3.
• Restore the intended layout and verify that all theme options, widgets, and built-in integrations work as they should.
• Provide a short summary of the changes made so I can keep future updates trouble-free.

Error Details
=============
An error of type E_ERROR was caused in line 1982 of the file /var/www/vhosts/green-orange-villa.com/httpdocs/wp-content/themes/wpnation/functions.php. Error message: Uncaught Error: Call to undefined function create_function() in /var/www/vhosts/green-orange-villa.com/httpdocs/wp-content/themes/wpnation/functions.php:1982
Stack trace:
#0 /var/www/vhosts/green-orange-villa.com/httpdocs/wp-settings.php(695): include()
#1 /var/www/vhosts/green-orange-villa.com/httpdocs/wp-config.php(97): require_once('...')
#2 /var/www/vhosts/green-orange-villa.com/httpdocs/wp-load.php(50): require_once('...')
#3 /var/www/vhosts/green-orange-villa.com/httpdocs/wp-admin/admin.php(35): require_once('...')
#4 /var/www/vhosts/green-orange-villa.com/httpdocs/wp-admin/index.php(10): require_once('...')
#5 {main}
thrown


Please be comfortable debugging custom themes and testing on a staging copy before touching the live site. Once the fix is confirmed, I’ll merge it to production.