title: PHP Detect page open via WebView
body: <p>I've a web page that has to be opened only via mobile app with <code>webview</code> (or anything the OS uses).</p>
  <p>I found some answer where people say to use <code>HTTP_USER_AGENT</code> to check where the request come from, but user-agent is easy editable during the request, so I'm looking for a safer way to do this.</p>
  <p>What could be the best approach in this case?</p>
  <p>Thank you</p>