PHP date example: get last week, this week, last month, this month, this quarter, last quarter

Example, php gets last week, this week, last month, this month, this quarter, and last quarter.

date_default_timezone_set('PRC');
date("Y-m-d H:i:s", strtotime(" +2 year"));
date("Y-m-d H:i:s ", strtotime(" +2 month"));
date("Y-m-d H:i:s", strtotime(" +2 week"));
date("Y-m-d H:i:s", strtotime(" + 2 day"));
date("Y-m-d H:i:s", strtotime(" +2 hour"));
date("Y-m-d H:i:s", strtotime(" +2 minute"));
date("Y-m-d H:i:s", strtotime(" +2 second"));

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";

echo "************" Month:";
echo date('n');
echo "************Day of the week:";
echo date("w");
echo "***** ****Days of this month:";
echo date("t");
echo "************";

echo 'Last week:';
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 'This week:';
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 'Last month:';
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 'This month:';
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";

$season = ceil((date('n'))/3);//Which quarter is this month?

echo 'This quarter:
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;//What quarter was the last quarter?

echo ' Last quarter:';
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";
?>