title: How to get referrer source of iframe parent page?
body: <p>We are taking our iframe entry form code and placing it on a website page. We want to be able to see where someone came from if they land on the page and entered their information into the form.</p>
  
  <p>For example: our iframe is embedded on a page. The URL of that page gets posted to Facebook. Someone clicks the link, lands on the page, and enters their information into our iframe entry form. We then want to be able to say, 1 referral came from Facebook.</p>
  
  <p>We tried using $_SERVER['HTTP_REFERER'], but this just returns the parent page URL of where the iframe is embedded, which we don't want. We want the actual URL of the referral to the parent page (in the example above, it would be Facebook). Is there anyway to grab this information?</p>