Rounding up expires param on PHP

gistfile1.aw

$roundup = 15 * 60; //Roundup time in seconds, 15 minutes
//Round up the expires time to 15 minutes unless otherwise specified
if (!array_key_exists('expires', $params)) {
  $params['expires'] = (floor(time()/$roundup) * $roundup) + $roundup;
}