php实现比较两个字符串日期大小的方法

<?php
function datebdate($date1, $date2) {
// 日期1是否大于日期2
 $month1 = date("m", strtotime($date1));
 $month2 = date("m", strtotime($date2));
 $day1 = date("d", strtotime($date1));
 $day2 = date("d", strtotime($date2));
 $year1 = date("y", strtotime($date1));
 $year2 = date("y", strtotime($date2));
 $from = mktime(0, 0, 0, $month1, $day1, $year1);
 $to = mktime(0, 0, 0, $month2, $day2, $year2);
 if ($from > $to) {
 return true;
 } else {
 return false;
 } 
} 
?>
$date1 = "2009-10-13";
$date= mktime(0, 0, 0, date("m", strtotime($date1)), date("d", strtotime($date1)), date("y", strtotime($date1)));

function datebcurrent($date){
//日期是否大于当前日期
 $currentdate=date("y-m-d");
 //获取当前日期
 $cyear=date("y",strtotime($currentdate));
 $cmonth=date("m",strtotime($currentdate));
 $cday=date("d",strtotime($currentdate));
 $year=date("y",strtotime($date));
 $month=date("m",strtotime($date));
 $day=date("d",strtotime($date));
 $currentunix=mktime(0,0,0,$cmonth,$cday,$cyear);
 //当前日期的 unix 时间戳
 $dateunix=mktime(0,0,0,$month,$day,$year);
 //待比较日期的 unix 时间戳
 if($dateunix<=$currentunix){
 return true;
 }else{
 return false;
 }
}