How do you make a proxy server that would proxy a site by doing to following: https://ift.tt/37VRtZx?

I want to make a proxy server that gets a URL from the user and proxies it to them. I don't want to have to hard code each proxied site. An example would be whoer.net, although it has recently been marked by Google Chrome as malicious. Currently, I have an apache2 website, hosted on Debian, that I would like this proxy server to be accessed from.