function getwhen($time) { 
  $when = date('Y-m-d', strtotime($time));
  $when = strtotime($when);
  $curr = strtotime(date("Y-m-d"));

  $date = $when - $curr;
  $diff = floor($date/(60*60*24));
 
  if($diff == 0): 
    echo 'today';
  elseif($diff > 1): 
    echo 'future time';
  elseif($diff > 0): 
    echo 'tomorrow';
  elseif($diff < -1): 
    echo 'back time';
  else: 
    echo 'yesterday';
  endif;
}
$date = '2020-04-24 10:00:00';
echo getwhen($date);