title: Embeding a web page and interact with it
body: <p>I want to develop a small registration page that other sites can host, so when the user enters their site, he actually sees my registration page. My page calls a PHP API with the relevant info (name, email, password) to save this info in the DB.</p>
  
  <p>Along with the above info, I want to add another parameter which is a unique ID of the site that host my registration page so when the user clicks on the Register button, his name, email and password are sent to the API (that is done inside my page already) along with a unique ID (of the site).</p>
  
  <p>The hosting itself can be done using iframe, or is there another/better option for that? The idea is that the site owner will get a code sample to copy paste in his site.</p>
  
  <p>How can I let the hosting site interact with my page in order to send it the site's unique ID?</p>