title: Rounding up to nearest available time slot in PHP
body: <p>I've been struggling with this for an hour or so and have come up blank. Basically I need to take the current time, add 30 minutes to it, and then round up to the next 15 minutes.</p>
  
  <p>Examples:</p>
  
  <ul>
  <li>if it's now 20:00, result = 20:45</li>
  <li>if it's now 20:10, result = 20:45</li>
  <li>if it's now 20:16, result = 21:00</li>
  <li>if it's now 20:35, result = 21:15</li>
  </ul>
  
  <p>My PHP is rusty and I've been getting mixed up with date add and round methods trying to get this to work and I know it's simple - have just run out of ideas!</p>
  
  <p>Thanks</p>