title: How to add leading zeros and commas to a number in PHP
body: <p>I have a variable <code>$counter</code> that returns the following integer:</p>
  
  <pre><code>4
  </code></pre>
  
  <p>I want to use number format or similar to make my integer appear in this format:</p>
  
  <pre><code>000,000,004
  </code></pre>
  
  <p>How can I this be done?</p>