用php获取本周,上周,本月,上月,本季度日期的代码

用php获取本周,上周,本月,上月,本季度日期的代码,主要用到date,strtotime和mktime函数.
echo date("Ymd",strtotime("now")), "<br />";
echo date("Ymd",strtotime("-1 week Monday")), "<br />";
echo date("Ymd",strtotime("-1 week Sunday")), "<br />";
echo date("Ymd",strtotime("+0 week Monday")), "<br />";
echo date("Ymd",strtotime("+0 week Sunday")), "<br />";
//date("m") 第几个月
//date("w") 本周周几
//date("t") 本月天数
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"))),"<br />";
echo date("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("d")-date("w")+7-7,date("Y"))),"<br />";
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"))),"<br />";
echo date("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("d")-date("w")+7,date("Y"))),"<br />";
echo "<br>上月:<br>";
echo date("Y-m-d H:i:s",mktime(0, 0 , 0,date("m")-1,1,date("Y"))),"<br />";
echo date("Y-m-d H:i:s",mktime(23,59,59,date("m") ,0,date("Y"))),"<br />";
echo "<br>本月:<br>";
echo date("Y-m-d H:i:s",mktime(0, 0 , 0,date("m"),1,date("Y"))),"<br />";
echo date("Y-m-d H:i:s",mktime(23,59,59,date("m"),date("t"),date("Y"))),"<br />";
$getMonthDays = date("t",mktime(0, 0 , 0,date("n")+(date("n")-1)%3,1,date("Y")));//本季度未最后一月天数
echo "<br>本季度:<br>";
echo date('Y-m-d H:i:s', mktime(0, 0, 0,date('n')-(date('n')-1)%3,1,date('Y'))),"<br />";
echo date('Y-m-d H:i:s', mktime(23,59,59,date('n')+(date('n')-1)%3,$getMonthDays,date('Y'))),"<br />";