<?
$birthday="1911-05-03";
$birthday=date("Y")."-".date("m",strtotime($birthday))."-".date("d",strtotime($birthday));
$start_date = date("Y-m-d", strtotime('last day of -1 month', strtotime($birthday)) );
$end_date = date("Y-m-d", strtotime('last day of 0 month', strtotime($birthday)) );
?>
<p><?echo "$start_date";?></p>
<p><?echo "$end_date";?></p>
這樣嗎?

我測試一下，感謝您的回覆

$birthday轉$birthday太厲害了 奇葩無誤