title: One long-lasting AJAX request and site switch within one PHP session
body: <h2>Introduction</h2>
  
  <p>I am writing a WordPress plugin, but I think it is more a PHP/Apache question. The WordPress plugin requests every 60 seconds (or at startup of each site) an AJAX call to the WordPress backend. If something conditional is true the request can be up to 20 seconds (depending on <code>max_execution_time</code>).</p>
  
  <h2>The problem</h2>
  
  <p>Adopted the AJAX request now starts and the process takes 20 seconds, but now I want to switch the WordPress site <strong>before the AJAX request is finished</strong>. The site switch happens after the 20 seconds, but why? I am using Apache Server.</p>
  
  <p>I hope it is well explained. :-)</p>