title: Add space after every 4th character
body: <p>I want to add a space to some output after every 4th character until the end of the string.
  I tried:</p>
  
  <pre><code>$str = $rows['value'];
  &lt;? echo substr($str, 0, 4) . ' ' . substr($str, 4); ?&gt;
  </code></pre>
  
  <p>Which just got me the space after the first 4 characters.</p>
  
  <p>How can I make it show after every 4th ?</p>