title: How to get the total hour from starting time to end time in php
body: <p>How can I get the total hour from start time to end time.</p>
  
  <pre><code>   $start_time = '11:00:00 PM'; // as of 07/08/2013
     $end_time   = '01:00:00 AM'; // as of 08/08/2013
  </code></pre>
  
  <p>Then output should be:</p>
  
  <pre><code>   $total = '02:00:00'; // 12 hour format
  </code></pre>