PHP获取某年某月开始和结束的时间戳

1/**
2 * 月份开始结束时间戳
3 * $y 年
4 * $m 月
5 */
6function mFristAndLast($y = "", $m = "")
7{
8    if ($y == "") $y = date("Y");
9    if ($m == "") $m = date("m");
10    $m = sprintf("%02d", intval($m));
11    $y = str_pad(intval($y), 4, "0", STR_PAD_RIGHT);
12
13    $m > 12 || $m < 1 ? $m = 1 : $m = $m;
14    $firstday = strtotime($y . $m . "01000000");
15    $firstdaystr = date("Y-m-01", $firstday);
16    $lastday = strtotime(date('Y-m-d 23:59:59', strtotime("$firstdaystr +1 month -1 day")));
17
18    return array(
19        "firstday" => $firstday,
20        "lastday" => $lastday
21    );
22}