title: How to detect if an user clicked on refresh button or F5 or Ctrl+F5?
body: <p><strong>Edit:</strong> Is it a good thing to use?</p>
  
  <pre><code>window.onbeforeunload = function(e) {
  
  };
  </code></pre>
  
  <p>In this function I should detect if user click refresh and if YES then do this: <code>$_POST['enter'] = NULL;</code></p>