function first_last_day($string, $first_last, $format) {
    $result = strtotime($string);
    $year = date('Y',$result);
    $month = date('m',$result);
    $result = strtotime("{$year}-{$month}-01");
    if ($first_last == 'last'){$result = strtotime('-1 second', strtotime('+1 month', $result)); }
    if ($format == 'unix'){return $result; }
    if ($format == 'standard'){return date('Y-m-d', $result); }
}

http://zkinformer.com/?p=134

T返回给定日期当月的天数(date参见文档):

$a_date = "2009-11-23";
echo date("Y-m-t", strtotime($a_date));

这应该可以工作:

$week_start = strtotime('last Sunday', time());
$week_end = strtotime('next Sunday', time());

$month_start = strtotime('first day of this month', time());
$month_end = strtotime('last day of this month', time());

$year_start = strtotime('first day of January', time());
$year_end = strtotime('last day of December', time());

echo date('D, M jS Y', $week_start).'<br/>';
echo date('D, M jS Y', $week_end).'<br/>';

echo date('D, M jS Y', $month_start).'<br/>';
echo date('D, M jS Y', $month_end).'<br/>';

echo date('D, M jS Y', $year_start).'<br/>';
echo date('D, M jS Y', $year_end).'<br/>';

我知道这有点晚了，但我认为有一种更优雅的方式来使用PHP 5.3+使用DateTime类:

$date = new DateTime('now');
$date->modify('last day of this month');
echo $date->format('Y-m-d');

您也可以将它与datetime一起使用

$date = new \DateTime();
$nbrDay = $date->format('t');
$lastDay = $date->format('Y-m-t');

你可以为下个月的第一天创建一个日期，然后使用strtotime("-1 day"， $firstOfNextMonth)