(string) Used to create WP nonce for verification on PHP callback.
$action
The name of the Ajax action.
$php_callback
PHP function to respond to ajax calls.
$script_path
The path where the JavaScript file is located.
$mode
(string) Determines if the script will be exposed to authenticated Ajax actions for logged-in users or non-authenticated Ajax actions for logged-out users or both. Using both, private, and public.