I tried installed Ultimate DebugBar on WP with Divi theme builder. The server crashed with error log:

PHP Fatal error:  Uncaught Error: Call to undefined function et_core_cache_dir() in /var/www/wp-content/themes/Divi/includes/builder/feature/AjaxCache.php:236
Stack trace:
#0 /var/www/wp-content/themes/Divi/includes/builder/feature/AjaxCache.php(62): ET_Builder_Ajax_Cache->get_file_name()
#1 /var/www/wp-content/themes/Divi/includes/builder/feature/AjaxCache.php(177): ET_Builder_Ajax_Cache->file_exists()
#2 /var/www/wp-content/themes/Divi/includes/builder/feature/AjaxCache.php(124): ET_Builder_Ajax_Cache->delete_file()
#3 /var/www/wp-content/themes/Divi/includes/builder/feature/AjaxCache.php(137): ET_Builder_Ajax_Cache->load()
#4 /var/www/wp-includes/class-wp-hook.php(307): ET_Builder_Ajax_Cache->save()
#5 /var/www/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters()

I know nothing about WordPress, do you know the root cause?
I deleted the plugin folder and the entry in the wp_options table and the site was live again, so it is for sure the Ultimate DebugBar plugin that introduces this error.

Thank you

Hi,
I’m working on optimization of website WooCommerce based. Your plugin is awesome, and it helps me to understand where I can operate in order to speed up my website.

I’m trying to understand what “Preparing data to render” is defined, in “Timeline” tab.
Which are all requests made in this section?

Thanks in advantage for your supply.