Online PHP editor | output for a1WLk

<?php $datetimeStart1 = new DateTime('2015-12-10'); $datetimeStart1 = $datetimeStart1->format('U'); $datetimeEnd1 = new DateTime('2015-12-20'); $datetimeEnd1 = $datetimeEnd1->format('U'); $datetimeStart2 = new DateTime('2015-12-12'); $datetimeStart2 = $datetimeStart2->format('U'); $datetimeEnd2 = new DateTime('2015-12-28'); $datetimeEnd2 = $datetimeEnd2->format('U'); // following http://stackoverflow.com/questions/325933/determine-whether-two-date-ranges-overlap if ($datetimeStart1 < $datetimeEnd2 && $datetimeEnd1 > $datetimeStart2) { echo round( ((min($datetimeEnd1,$datetimeEnd2)) - (max($datetimeStart2,$datetimeStart1))) / (60*60*24)) + 1; } else { echo 'no overlap'; }