title: Calculate business days
body: <p>I need a method for adding "business days" in PHP. For example, Friday 12/5 + 3 business days = Wednesday 12/10.</p>
  
  <p>At a minimum I need the code to understand weekends, but ideally it should account for US federal holidays as well. I'm sure I could come up with a solution by brute force if necessary, but I'm hoping there's a more elegant approach out there. Anyone?</p>
  
  <p>Thanks.</p>