IP addresses can't likely be harvested from your PHP code because the web server will execute the PHP script and only send the result to the browser.
But there are lots of bots that just scan random IP addresses on port 80 and look for vulnerable software, often using Google's user agent string - did you check if the request's IP address actually belongs to Google? There is even a search engine for IP addresses that have web servers running, you could check if you can find your own host: http://www.shodanhq.com
It is generally a bad idea to let a development server listen on 0.0.0.0, i.e. expose it to the Internet. If you don't need to access it from the outside, let it listen on 127.0.0.1 or you could run into trouble if you don't update it often.