Displaying the first Google result

I’m working on a page that displays the first search result in Google.
So let’s say you visit [url]www.mydomain.com/?q=John+Doe[/url] you are redirected to [url]www.google.com/?q=John+Doe[/url].
This is already working fine, but here’s the question:

I would like it to redirect to the first result, instead of the results page.
So if /?q=John+Doe points to [url]www.johndoe.com[/url], redirect to there.

How can I isolate and interpret that first result?
Returning the URL of the first result is what I’m looking for.

Thanks!

PS. I’m working in PHP and JavaScript/AJAX.

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