Proxy Detector is a PHP class that can detect HTTP requests via proxy. This class can detect if a visitor uses a proxy server by scanning the headers returned by the user client. When the user uses a proxy server, most of the proxy servers alter the header. The header is returned to PHP in the array $_SERVER.
Whoisdomaincheckup is a Web-based (PHP) application that can check the registration status of a domain name. In particular, it can check whether a domain name is currently free for registration. It doesn't use any exec or system commands, but instead uses the fopen command to access the Whois servers.