Save button disappears when PHP version 8.1

An error of type E_ERROR was caused in line 685 of the file /home/caviarof/public_html/wp-content/plugins/litespeed-cache/src/base.cls.php. Error message: Uncaught Error: Call to undefined function LiteSpeed\parse_ini_file() in /home/caviarof/public_html/wp-content/plugins/litespeed-cache/src/base.cls.php:685

Stack trace:

#0 /home/caviarof/public_html/wp-content/plugins/litespeed-cache/src/admin-display.cls.php(1024): LiteSpeed\Base->load_default_vals()

#1 /home/caviarof/public_html/wp-content/plugins/litespeed-cache/tpl/page_optm/settings_media.tpl.php(79): LiteSpeed\Admin_Display->recommended()

#2 /home/caviarof/public_html/wp-content/plugins/litespeed-cache/tpl/page_optm/entry.tpl.php(54): require('...')

#3 /home/caviarof/public_html/wp-content/plugins/litespeed-cache/src/admin-display.cls.php(678): require_once('...')

#4 /home/caviarof/public_html/wp-includes/class-wp-hook.php(308): LiteSpeed\Admin_Display->show_page_optm()

#5 /home/caviarof/public_html/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters()

#6 /home/caviarof/public_html/wp-includes/plugin.php(517): WP_Hook->do_action()

#7 /home/caviarof/public_html/wp-admin/admin.php(259): do_action()

#8 {main}

  thrown

please make sure you did NOT disable function parse_ini_file

The problem persists even when enabling function parse_ini_file

<?php
require( './wp-load.php' );
if (function_exists('parse_ini_file')) {
   echo 'yes';
}
else {
    echo 'no';
}

could you please try create a php file with above code at same dir as your wp-config.php , access by browser, and see what it returns ?

no

https://caviarofswitzerland.com/testlite.php

yeah , that means theparse_ini_file function was NOT enabled