如何查找给定日期所属一周的第一天？

Question

可能的重复：
用 PHP 获取一周的第一天？

给定一个时间戳，我需要查找时间戳所属周的第一天。

例如，

$format = "first day of week";

//convert to time
$time = strtotime("2011-07-01 00:00:00");

//format the time to the first day of the week
$date = strtotime($format,$time);

//Put the first day of the week into a pretty format
$weekStartDate = date("Y-m-d",$date);

一周的开始应该等于 2011-06-27，此时它出了严重的错误，等于 1970-01-01，这对我来说意味着“一周的第一天”格式是无效的。

任何想法将不胜感激，谢谢，

Answer 1

$time = strtotime("2011-07-01 00:00:00");

$weekStartDate = date('Y-m-d',strtotime("last Monday", $time));

Answer 2

测试一下：

$time=[Your Request Time];

$dayofweek = date("w",strtotime($time));

if( $dayofweek != 0  )

    $firstdayOfWeek = strtotime( $time . " - " . $dayofweek . " days " );

else

    $firstdayOfWeek = strtotime($time);