title: PHP - Source (hostname) of a GET request
body: <p>I have a Javascript widget that people can embed on their site. </p>
  
  <p>I want to use a simple cross domain get request to pull in a hash. </p>
  
  <p>However I need my PHP script to only allow this cross domain request from a series of domains I have stored in an array. </p>
  
  <p>What can I do in my PHP script (not in <code>.htaccess</code>or iptables) to find out the source (hostname) of the get request?</p>