<?php
        
$week_begin = mktime(0, 0, 0,date("m"),date("d")-date("w")+1,date("Y"));
$week_end = mktime(23,59,59,date("m"),date("d")-date("w")+7,date("Y"));

echo $week_begin.'==='.date('y-m-d H:i:s',$week_begin);
echo '<br />';
echo $week_end.'==='.date('y-m-d H:i:s',$week_end);
echo '<br />';


echo date("Ymd",strtotime("now")), "\n";   
echo date("Ymd",strtotime("-1 week Monday")), "\n";   
echo date("Ymd",strtotime("-1 week Sunday")), "\n";   
echo date("Ymd",strtotime("+0 week Monday")), "\n";   
echo date("Ymd",strtotime("+0 week Sunday")), "\n";   
 
 
//date('n') 第几个月   
//date("w") 本周周几   
//date("t") 本月天数   
 
echo '<br>本日:<br>';   
echo date("Y-m-d H:i:s",mktime(0, 0, 0,date("m"),date("d"),date("Y"))),"\n";   
echo '<br>上周:<br>';   
echo date("Y-m-d H:i:s",mktime(0, 0, 0,date("m"),date("d")-date("w")+1-7,date("Y"))),"\n";   
echo date("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("d")-date("w")+7-7,date("Y"))),"\n";   
echo '<br>本周:<br>';   
echo date("Y-m-d H:i:s",mktime(0, 0, 0,date("m"),date("d")-date("w")+1,date("Y"))),"\n";   
echo date("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("d")-date("w")+7,date("Y"))),"\n";   
 
echo '<br>上月:<br>';   
echo date("Y-m-d H:i:s",mktime(0, 0, 0,date("m")-1,1,date("Y"))),"\n";   
echo date("Y-m-d H:i:s",mktime(23,59,59,date("m")  ,0,date("Y"))),"\n";   
echo '<br>本月:<br>';   
echo date("Y-m-d H:i:s",mktime(0, 0, 0,date("m"),1,date("Y"))),"\n";   
echo date("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("t"),date("Y"))),"\n";   
 
$getMonthDays = date("t",mktime(0, 0, 0,date('n')+(date('n')-1)%3,1,date("Y")));//本季度未最后一月天数   
echo '<br>本季度:<br>';   
echo date('Y-m-d H:i:s', mktime(0, 0, 0,date('n')-(date('n')-1)%3,1,date('Y'))),"\n";   
echo date('Y-m-d H:i:s', mktime(23,59,59,date('n')+(date('n')-1)%3,$getMonthDays,date('Y'))),"\n";

$season = ceil((date('n'))/3);//当月是第几季度
echo '<br>本季度:<br>';
echo date('Y-m-d H:i:s', mktime(0, 0, 0,$season*3-3+1,1,date('Y'))),"\n";
echo date('Y-m-d H:i:s', mktime(23,59,59,$season*3,date('t',mktime(0, 0 , 0,$season*3,1,date("Y"))),date('Y'))),"\n";
 
$season = ceil((date('n'))/3)-1;//上季度是第几季度
echo '<br>上季度:<br>';
echo date('Y-m-d H:i:s', mktime(0, 0, 0,$season*3-3+1,1,date('Y'))),"\n";
echo date('Y-m-d H:i:s', mktime(23,59,59,$season*3,date('t',mktime(0, 0 , 0,$season*3,1,date("Y"))),date('Y'))),"\n";

 
php两个日期相减得天数
<?php
function count_days($a,$b){
 $a_dt=getdate($a);
 $b_dt=getdate($b);
 $a_new=mktime(12,0,0,$a_dt['mon'],$a_dt['mday'],$a_dt['year']);
 $b_new=mktime(12,0,0,$b_dt['mon'],$b_dt['mday'],$b_dt['year']);
 return round(abs($a_new-$b_new)/3600/24);
}
    function count_days($formdate,$todate){
        return round(abs(strtotime($formdate)-strtotime($todate))/3600/24);

    }

?>