Help with Fatal error: Uncaught TypeError: number_format() expects parameter 1

I am using a php web script that all works successfully. But when I added this:

declare( strict_types=1);
error_reporting(-1);
ini_set('display_errors' , 'true');
PHP:

I now see this:

Fatal error: Uncaught TypeError: […]

See original post by invalid@example.com (chrisj)