title: What is a good way to generate short and unique file/folder names?
body: <p>The criteria is basically this:</p>
  
  <ul>
  <li>folders will exist for about 24-48hrs</li>
  <li>folders names can not be readily guessable by a user (if used in a URL)</li>
  <li>folder names should be short 5-15 chars</li>
  </ul>
  
  <p>Initial thoughts:</p>
  
  <pre><code>printf('%u',crc32(microtime(true)));
  </code></pre>
  
  <p>Details:
  When uploading a file, I basically want to keep the unique file name as named by the uploader, so to avoid any naming collision I would like to put it in a uniquely named directory ... </p>