I'm getting this error as of recently, running leproxy-0.2.2 with PHP 7.3.29 on macOS Monterey:

Fatal error: Uncaught Error: Call to undefined function LeProxy\LeProxy\filter_var() in /leproxy-0.2.2.php:2448

It has been working for me a couple of weeks ago (potentially before the macOS update to Monterey). Any ideas what the problem could be? Probably it's related to my environment, rather than leproxy itself. Am I missing any requirements?