title: Get the url of an external iframe
body: <p>I want to retrive the url of an external <code>iframe</code>.</p>
  
  <p>The url I can see in my browser, but how can I get the url of that what can I see in the browser via JS or PHP?</p>
  
  <ul>
  <li><p><strong>Preview Image 1 :</strong>
  <img src="https://i.stack.imgur.com/KiayR.png" alt="enter image description here"></p></li>
  <li><p><strong>Preview Image 2 :</strong>
  <img src="https://i.stack.imgur.com/QHUwh.png" alt="enter image description here"></p></li>
  </ul>
  
  <p>After I click the blue hovered firefox menu item in Preview Image 1, I get the results that I want in firefox.</p>
  
  <p>How to obtain this in JS?</p>