why we use 'final',could you give me an example in real world?
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/526312/when-should-i-use-final">When should I use &ldquo;final&rdquo;?</a>  </p>
</blockquote>



<p>PHP has a keyword 'final', 
Could you give me an example in real world that use this keyword.</p>

<p>I just don't know when to use.</p>
