function date_diff($date1,$date2) {

   $tmp_date1 = explode("-",$date1);

   $tmp_date2 = explode("-", $date2);

   $tmp1 = mktime(0,0,0,$tmp_date1[1], $tmp_date1[2], $tmp_date1[0]);

   $tmp2 = mktime(0,0,0,$tmp_date2[1], $tmp_date2[2], $tmp_date2[0]);

   $return_date = ($tmp1 - $tmp2) / 86400;

   return $return_date;

}

$Today = date('Y-m-d');

$diff_day = date_diff('날짜',$Today);

if($diff_day > 0) {

   echo "날짜가 큰 날임.";

} else {

   echo "날짜가 작은 날임.";

}