title: How to prevent viewing two pages in same time
body: <p>I've media website once member is logged successfully it creates session</p>
  
  <pre><code>$_SESSION['login_id'] = $username;
  </code></pre>
  
  <p>I wonder how to prevent members to watch two channels in same time.</p>
  
  <p>I mean for example if member is viewing page <code>video.php?id=4</code> and open in new tab page <code>video.php?id=5</code> it shows him error have to close the page of <code>video.php?id=4</code> before viewing the new page.</p>
  
  <p>1st thing came into my mind is random <code>token key</code> that cleared on page exit but i don't know if it good idea or not, does anyone known how to do it or have better idea ! ~ thanks</p>