title: How to get the file name under a folder?
body: <p>Suppose I have a directory look like:</p>
  
  <pre><code>ABC
  |_ a1.txt
  |_ a2.txt
  |_ a3.txt
  |_ a4.txt
  |_ a5.txt
  </code></pre>
  
  <p>How can I use PHP to get these file names to an array, limited to a specific file extension and ignoring directories?</p>