title: Page cache in PHP that handles concurrency?
body: <p>I've read previous answers here about caching in PHP, and the articles they link to.  I've checked out the oft-recommended <a href="http://pear.php.net/package/Cache_Lite" rel="noreferrer">Pear Cache_Light</a>, QuickCache, and WordPress Super Cache.  (Sorry - apparently I'm allowed to hyperlink only once.)</p>
  
  <p>Either none deal with concurrency issues, or none explicitly call out that they do in their documentation.</p>
  
  <p>Can anyone point me in the direction of a PHP page cache that handles concurrency?</p>
  
  <p>This is on a shared host, so memcache and opcode caches are unfortunately not an option.  I don't use a templating engine and would like to avoid taking a dependency on one.  WP Super Cache's approach is preferable - i.e. storing static files under wwwroot to let Apache serve them - but not a requirement.</p>
  
  <p>Thanks!</p>
  
  <p>P.S. Examples of things that should be handled automatically:</p>
  
  <ol>
  <li>Apache / the PHP cache is in the middle of reading a cached file.  The cached file becomes obsolete and deletion is attempted.</li>
  <li>A cached file was deleted because it was obsolete.  A request for that file comes in, and the file is in the process of being recreated.  <em>Another</em> request for the file comes in during this.</li>
  </ol>