How to implement a proxy site in PHP?

Like this one:

https://aniscartujo.co开发者_运维问答m/webproxy/default.aspx?prx=http://google.com

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Check out PHProxy: http://lifehacker.com/5447726/install-phproxy-in-your-web-space-to-access-blocked-sites

Download: http://sourceforge.net/projects/poxy/

I have actually used this at high school on my site: http://bypass.provanix.com/ and added a login.

Edit:

If you want to try it out, login with username "default" and password "default". I'm still working on the YouTube workaround - it used to work, but the site changed.

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<form><input name=url><input type=submit></form>

Once the form is submitted you'll receive in your php a post variable named "url" where the user has typed the url to surf, the simple way to implement in php is:

echo file_get_contents($_POST['url']);

NB: in order to use file_get_contents properly you should have allow_url_fopen enabled in you php.ini

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Using squid with a custom url-rewriter (maybe written in PHP) would provide all the required functionality - why start from scratch?