title: ETAG -How to set expiration time?
body: <p>I was try to set ETAG in my PHP page using the following code,</p>
  
  <pre><code>$time       = strtotime(date('Y-m-d H:i:').'00');
  $lastmod    = gmdate('D, d M Y H:i:s \G\M\T', $time);
  $etag       = '123';
  $ifmod      = isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) ?   $_SERVER['HTTP_IF_MODIFIED_SINCE'] == $lastmod : null; 
  $iftag      = isset($_SERVER['HTTP_IF_NONE_MATCH']) ? $_SERVER['HTTP_IF_NONE_MATCH'] ==      $etag : null; 
  
  if (($ifmod || $iftag) &amp;&amp; ($ifmod !== false &amp;&amp; $iftag !== false)) { 
    header('HTTP/1.0 304 Not Modified');
    die;
  } else {
    header("Last-Modified: $lastmod"); 
    header("ETag: $etag");
    echo "My Page content";
  }
  </code></pre>
  
  <p>I write this code for caching enable for one minute,But it is not perfect ,because<br>
  <code>strtotime(date('Y-m-d H:i:').'00');</code> is not give a absolute one minute interval.</p>
  
  <p>Is there any other solution?</p>