title: Calculate number of hours between 2 dates in PHP
body: <p>How do I calculate the difference between two dates in hours?</p>
  
  <p>For example:</p>
  
  <pre><code>day1=2006-04-12 12:30:00
  day2=2006-04-14 11:30:00
  </code></pre>
  
  <p>In this case the result should be 47 hours.</p>