title: PHP count, add colons every 2 characters
body: <p>I have this string</p>
  
  <pre><code>1010081-COP-8-27-20110616214459
  </code></pre>
  
  <p>I need to count the last 6 characters starting from the end of this string (because it could may be long starting from the begin)</p>
  
  <p>Then I need to add colons after every 2 characters.</p>
  
  <p>So after counting 6 characters from the end it will be </p>
  
  <pre><code>214459
  </code></pre>
  
  <p>After having added the colons it will look like:</p>
  
  <pre><code>21:44:59
  </code></pre>
  
  <p>Can you help me achieving it?</p>
  
  <p>I do not really know where to start!</p>
  
  <p>Thank you</p>