PHP time and date processing and sorting

 //Return the timestamps of all months in a time period

function monthList($start,$end){
 if(!is_numeric($start)||!is_numeric($end)||($end< ;=$start)) return '';
 $start=date('Y-m',$start);
 $end=date('Y-m',$end);
 //Convert to timestamp
 $start=strtotime($start.'-01');
 $end=strtotime($end.'-01');
 $i=0;
 $d=array();
 while($start<= $end){
 //The calculation formula for the total number of seconds accumulated in each month is: the timestamp seconds on the 1st of the previous month minus the timestamp seconds of the current month
 $d[$i]=trim(date ('Y-m',$start),' ');
 $start+=strtotime('+1 month',$start)-$start;
 $i++;
 }
 return $d;

 }

 //Return the start and end dates of the week within a time period by passing date type

function monthList($start,$end){
 if(!is_numeric($start)||!is_numeric($end)||($end< ;=$start)) return '';
 $start=date('Y-m',$start);
 $end=date('Y-m',$end);
 //Convert to timestamp
 $start=strtotime($start.'-01');
 $end=strtotime($end.'-01');
 $i=0;
 $d=array();
 while($start<= $end){
 //The calculation formula for the total number of seconds accumulated in each month is: the timestamp seconds on the 1st of the previous month minus the timestamp seconds of the current month
 $d[$i]=trim(date ('Y-m',$start),' ');
 $start+=strtotime('+1 month',$start)-$start;
 $i++;
 }
 return $d;
 }

/ /Return the first and last day of a month

function getthemonth($date)
{
$firstday = date('Y-m-01', strtotime($date));
$lastday = date('Y-m-d ', strtotime("$firstday +1 month -1 day"));
return array($firstday,$lastday);
}
$today = date("Y-m-d");
$day=getthemonth($today) ;

PHP