Write transparent HTTP Proxy script in PHP

Is there an easy forwarding/transparent php proxy script that I can host on my web server? These are my conditions:

1. I'm using free web hosting, so I have pretty much no control over my machine. Otherwise I could use Perl's HTTP::Proxy module. This means no root password. It does run php though.

2. I already have a server running on port 80. What I mean is I would like to put a php script as index.php on my server that will forward all requests.

3. I don't want a script like PHProxy or Glype where I go to the site, then enter a URL. I want a server so I can enter proxy.example.com:80 in Firefox's or IE's or whatever's proxy settings and it will forward all requests to the server.

4. Preferably (though not fatal if not possible) I would like for it to pass on the USER_AGENT environmental variable (That's the browser) instead of setting itself to be the USER_AGENT

5. I can't start a new Daemon. My开发者_如何学C server won't allow it.

Is there a script that will do this? If so, which?

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No, I'm fairly sure this is not possible on shared hosting. It will fail your condition number 3. This needs support on web server level (e.g. using Apache's mod_proxy)

For this to work, you would have to set up the remote server to be able to deal with proxied requests. No sane web server will offer that possibility.