This has a few issues that need fixing, this URL Proxy is similar but yours has these issues
When Clicking a link it leaves the proxy <---- This is a Massive Issue
In the Source you can see that all links in there still is the base site (Like in Github, "https://github.githubassets.com/favicons/favicon.svg" we need it to be like "PHPproxySite.com/?u=https://github.githubassets.com/favicons/favicon.svg"), which will make the proxy work correct in locked URls, This will Fix the 1st issue
And in the page code sometimes you have a "/code.css" we need to get that file url so its like "website.com/css/code.css"
i hope i worded this correctly, its 2:27Am Rn