PHP 本周一开始的时间戳，周日结束的时间戳算法

卫哥的fashion版本：

$today = strtotime('today'); // 今天
$day = date('w', $today);
$begin = strtotime('-'. ($day+6)%7 .'days', $today);
$end = strtotime('+'. (7-$day)%7 .'days', $today)+86399;

我的super版本：

版本一：

// $time = strtotime('2021-04-3'); 指定某天
$time = strtotime('today'); // 今天

$week = date('w', $time);
if ($week == 0) {
    $week_start = mktime(0, 0, 0, date('m', $time), date('d', $time) - 6, date('Y', $time));
    $week_end = mktime(23, 59, 59, date('m', $time), date('d', $time), date('Y', $time));
} else {
    $week_start = mktime(0, 0, 0, date('m', $time), date('d', $time) - ($week - 1), date('Y', $time));
    $week_end = mktime(23, 59, 59, date('m', $time), date('d', $time) + (7 - $week), date('Y', $time));
}

版本二：

// $time = strtotime('2021-04-3'); 指定某天
$time = strtotime('today'); // 今天

$week = date('w', $time);
$week_start = mktime(0, 0, 0, date('m', $time), date('d', $time) - ((7 + (($week % 7) - 1)) % 7), date('Y', $time));
$week_end = mktime(23, 59, 59, date('m', $time), date('d', $time) + ((7 - $week) % 7), date('Y', $time));

笔记：错位求模