date difference

$ddate1=get_field(start_date,get_the_ID());
$ddate1=date('Ymd', strtotime($ddate1));
$ddate2=date('Ymd');
$ddate2=date('Ymd', strtotime($ddate2));
if ($ddate1 < $ddate2)
    {
      echo "old trip";
    }
    else
    {
      echo "new trip";
    }