Is there code that can grab content from a website and log it to a file?

I'm looking for some kind of script or code that can do the following:

Whenever a person visits: http://mysite.com/file.php it'll secretly load the link of another website http://targetsite.com and grab the entire content on the page based on what the visitor would see if he had visited http://targetsite.com directly.

It would log the content on my server as a .txt file or something like that

Heres a diagram to make it more clear:

http://i.imgur.com/SwYAE.png

Looks a little like scraping someone elses site. Without going in to the moral aspects of this it really wouldn't benefit your new site at all and probably will peanalise it as the search engines are hot on dupicate content and particularly don't like scraping for content.