PHP - strtotime()的慎用

strtotime('-X month')有可能会导致错误

获取正确的方法如下

<?php

date_default_timezone_set('Asia/Shanghai');

$first_day_of_month = date('Y-m',time());
$t = strtotime($first_day_of_month);

echo date("Y-m-01 00:00:00",strtotime('-1 month',$t)).'<br>';
echo date("Y-m-01 00:00:00",strtotime('-2 month',$t)).'<br>';
echo date("Y-m-01 00:00:00",strtotime('-3 month',$t)).'<br>';
echo date("Y-m-01 00:00:00",strtotime('-4 month',$t)).'<br>';
echo date("Y-m-01 00:00:00",strtotime('-5 month',$t)).'<br>';
echo date("Y-m-01 00:00:00",strtotime('-6 month',$t)).'<br>';