php gets the timestamp of the first and last day of this week, month

<?php
$start = mktime(0,0,0,date("m"),date("d"),date("Y")); 
$end = mktime(0,0,0,date("m"),date("d")+1,date("Y")); 

<?php
$year = date("Y");
$month = date("m");
$day = date('w');
$nowMonthDay = date("t");

$firstday = date('d') - $day;
if(substr($firstday,0,1) == "-"){
 $firstMonth = $month - 1;
 $lastMonthDay = date("t",$firstMonth);
 $firstday = $lastMonthDay - substr($firstday,1);
 $time_1 = strtotime($year."-".$firstMonth."-".$firstday);
}else{
 $time_1 = strtotime($year."-".$month."-".$firstday);
}
  
$lastday = date('d') + (7 - $day);
if($lastday > $nowMonthDay){
 $lastday = $lastday - $nowMonthDay;
 $lastMonth = $month + 1;
 $time_2 = strtotime($year."-".$lastMonth."-".$lastday);
}else{
 $time_2 = strtotime($year."-".$month."-".$lastday);
}

<?php
$year = date("Y");
$month = date("m");
$allday = date("t");
$strat_time = strtotime($year."-".$month."-1");
$end_time = strtotime($year."-".$month."-".$allday);