当月と前月の初めと終わりのタイムスタンプを取得する PHP メソッド

<?php
$thismonth = date(&#39;m&#39;);
$thisyear = date(&#39;Y&#39;);
$startDay = $thisyear . &#39;-&#39; . $thismonth . &#39;-1&#39;;
$endDay = $thisyear . &#39;-&#39; . $thismonth . &#39;-&#39; . date(&#39;t&#39;, strtotime($startDay));
$b_time  = strtotime($startDay);//当前月的月初时间戳
$e_time  = strtotime($endDay);//当前月的月末时间戳

<?php
$thismonth = date(&#39;m&#39;);
$thisyear = date(&#39;Y&#39;);
if ($thismonth == 1) {
 $lastmonth = 12;
 $lastyear = $thisyear - 1;
} else {
 $lastmonth = $thismonth - 1;
 $lastyear = $thisyear;
}
$lastStartDay = $lastyear . &#39;-&#39; . $lastmonth . &#39;-1&#39;;
$lastEndDay = $lastyear . &#39;-&#39; . $lastmonth . &#39;-&#39; . date(&#39;t&#39;, strtotime($lastStartDay));
$b_time = strtotime($lastStartDay);//上个月的月初时间戳
$e_time = strtotime($lastEndDay);//上个月的月末时间戳