title: time night differential computation in PHP
body: <p>I'm having problems in getting the night differential of an employee. Night differential starts from 10pm to 6am.</p>
  
  <p>If an employee goes to work from 7pm to 5:30am there should be a night differential of 7 hours and 30 minutes.</p>
  
  <p>How can I compute this using PHP?</p>
  
  <p>Thank you very much.</p>