I'm writing a tool similar to www.proxy.org but with some features which I'd like to keep to myself for now. My concern is - how do I send off the user requested URL and selected proxy? I can't simply redirect them to www.theproxytheywant.com?url=www.google.com because most proxies don't allow that - instead they have client side javascript that first encrypts the URL and this mechanism is unique to each proxy type. So. How can I go about this? Thanks.
A lot of phproxy sites just encode their urls in Base64, so, for those, you could just encode the requested url in base64 as well. It might work for some.
Forget it, there is no way you can pass by that proxy protections on all proxies. Even proxy.org cannot do that. It would be more fair do send them to www.theproxytheywant.com when they click a proxy or else you would be just another leacher.
I run a number of phproxies and this is the first I have heard of JS being used to encrypt the URL. It is totally untrue for phproxy. All that is required is a simple form with post method submitting to the index.php of the proxy site. You can see an example at masterunblocker.com . The homepage is not a proxy but a blog. Take a look at the source code and you'll see.
As you have said, though it's unique each type of proxy script, it's the same with all proxy sites using the same type of script. Just download all the scripts and look for how they have implemented the URL encoding. This way you could counter-engineer it and *leech* all of them. Not to mention some proxy sites don't encode URLs at all.